Added missing scope qualifiers to assert statement code so that calls to these

macros compile when invoked outside dlib namespace.

dlib/assert.h

@@ -69,8 +69,8 @@ namespace dlib
 // messages.
 #ifdef DLIB_HAS_STATIC_ASSERT
     #define COMPILE_TIME_ASSERT(expression) static_assert(expression, "Failed assertion")
-    #define ASSERT_ARE_SAME_TYPE(type1, type2) static_assert(assert_types_match<type1,type2>::value, "These types should be the same but aren't.")
-    #define ASSERT_ARE_NOT_SAME_TYPE(type1, type2) static_assert(!assert_types_match<type1,type2>::value, "These types should NOT be the same.")
+    #define ASSERT_ARE_SAME_TYPE(type1, type2) static_assert(::dlib::assert_types_match<type1,type2>::value, "These types should be the same but aren't.")
+    #define ASSERT_ARE_NOT_SAME_TYPE(type1, type2) static_assert(!::dlib::assert_types_match<type1,type2>::value, "These types should NOT be the same.")
 #else
     #define COMPILE_TIME_ASSERT(expression) \
         DLIB_NO_WARN_UNUSED typedef char BOOST_JOIN(DLIB_CTA, __LINE__)[::dlib::compile_time_assert<(bool)(expression)>::value]