Forgot to add mark.h

include/mark.h

+#pragma once
+
+namespace YAML
+{
+	struct Mark {
+		Mark(): pos(0), line(0), column(0) {}
+		
+		static const Mark null() { return Mark(-1, -1, -1); }
+		
+		int pos;
+		int line, column;
+		
+	private:
+		Mark(int pos_, int line_, int column_): pos(pos_), line(line_), column(column_) {}
+	};
+}