Fixed many -Wreserved-id-macro warnings by fixing header guard spelling (#361)

* Fixed many -Wreserved-id-macro warnings by fixing header guard spelling

Removed leading underscore(s) from header guard spelling.  Used 2 regexes:

` _H5(.*)_H`
` __H5(.*)_H`

Applied case-insensitively to only .h files.

* Modified scripts that generate header files to not use underscore prefix

Interestingly, there was already no leading underscore in the trailing comment at the end of the file

* Fixed remaining -Wreserved-id-macro warning not caught by regex

c++/src/H5OcreatProp.h

@@ -12,8 +12,8 @@
  * help@hdfgroup.org.                                                        *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
-#ifndef __H5ObjCreatPropList_H
-#define __H5ObjCreatPropList_H
+#ifndef H5ObjCreatPropList_H
+#define H5ObjCreatPropList_H
 
 namespace H5 {
 
@@ -75,4 +75,4 @@ class H5_DLLCPP ObjCreatPropList : public PropList {
 }; // end of ObjCreatPropList
 } // namespace H5
 
-#endif // __H5ObjCreatPropList_H
+#endif // H5ObjCreatPropList_H