Flipped the include guard and the pragma, and don't use the pragma for early...

Flipped the include guard and the pragma, and don't use the pragma for early versions of gcc (< 3.4)

include/yaml-cpp/parser.h

-#pragma once
-
 #ifndef PARSER_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define PARSER_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "yaml-cpp/noncopyable.h"
 #include <ios>

include/yaml-cpp/stlemitter.h

-#pragma once
-
 #ifndef STLEMITTER_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define STLEMITTER_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include <vector>
 #include <list>

include/yaml-cpp/stlnode.h

-#pragma once
-
 #ifndef STLNODE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define STLNODE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include <vector>
 #include <map>

include/yaml-cpp/traits.h

-#pragma once
-
 #ifndef TRAITS_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define TRAITS_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 namespace YAML
 {

include/yaml-cpp/yaml.h

-#pragma once
-
 #ifndef YAML_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define YAML_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "yaml-cpp/parser.h"
 #include "yaml-cpp/node.h"

src/aliascontent.h

-#pragma once
-
 #ifndef ALIASCONTENT_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define ALIASCONTENT_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "content.h"
 

src/collectionstack.h

-#pragma once
-
 #ifndef COLLECTIONSTACK_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define COLLECTIONSTACK_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include <stack>
 #include <cassert>

src/content.h

-#pragma once
-
 #ifndef CONTENT_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define CONTENT_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "yaml-cpp/anchor.h"
 #include "yaml-cpp/exceptions.h"

src/contrib/graphbuilderadapter.h

 #ifndef GRAPHBUILDERADAPTER_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define GRAPHBUILDERADAPTER_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 #include <map>
 #include <stack>
 #include "yaml-cpp/eventhandler.h"

src/directives.h

-#pragma once
-
 #ifndef DIRECTIVES_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define DIRECTIVES_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include <string>
 #include <map>

src/emitterstate.h

-#pragma once
-
 #ifndef EMITTERSTATE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define EMITTERSTATE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "setting.h"
 #include "yaml-cpp/emittermanip.h"

src/emitterutils.h

-#pragma once
-
 #ifndef EMITTERUTILS_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define EMITTERUTILS_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "yaml-cpp/ostream.h"
 #include <string>

src/exp.h

-#pragma once
-
 #ifndef EXP_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define EXP_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "regex.h"
 #include <string>

src/indentation.h

-#pragma once
-
 #ifndef INDENTATION_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define INDENTATION_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "yaml-cpp/ostream.h"
 #include <iostream>

src/iterpriv.h

-#pragma once
-
 #ifndef ITERPRIV_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define ITERPRIV_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "ltnode.h"
 #include <vector>

src/ltnode.h

-#pragma once
-
 #ifndef LTNODE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define LTNODE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 namespace YAML
 {

src/map.h

-#pragma once
-
 #ifndef MAP_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define MAP_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include "content.h"
 #include <map>

src/nodebuilder.h

-#pragma once
-
 #ifndef NODEBUILDER_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define NODEBUILDER_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 #include "yaml-cpp/eventhandler.h"
 #include "ptr_stack.h"
 #include <map>

src/ptr_stack.h

-#pragma once
-
 #ifndef PTR_STACK_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define PTR_STACK_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 #include "yaml-cpp/noncopyable.h"
 #include <memory>
 #include <vector>

src/regex.h

-#pragma once
-
 #ifndef REGEX_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 #define REGEX_H_62B23520_7C8E_11DE_8A39_0800200C9A66
 
+#if !defined(__GNUC__) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
 
 #include <vector>
 #include <string>