[svn-r24189] Purpose: Fixed bug HDFFV-1060

Description:
    Changed header guards from single underscore to double underscore.
Platforms tested:
    Linux/32 2.6 (jam) - very minor
    Linux/64 2.6 (koala)/PGI compilers

c++/src/H5DataSet.h

@@ -16,8 +16,8 @@
 
 // Class DataSet inherits from AbstractDs and provides accesses to a dataset.
 
-#ifndef _H5DataSet_H
-#define _H5DataSet_H
+#ifndef __H5DataSet_H
+#define __H5DataSet_H
 
 #ifndef H5_NO_NAMESPACE
 namespace H5 {
@@ -120,4 +120,4 @@ class H5_DLLCPP DataSet : public H5Object, public AbstractDs {
 #ifndef H5_NO_NAMESPACE
 }
 #endif
-#endif
+#endif // __H5DataSet_H