ENH: Classify a file as source or header even when the extension is given

explicitly.

Source/cmSourceFile.cxx

@@ -91,7 +91,11 @@ void cmSourceFile::SetName(const char* name, const char* dir,
 	}
       }
 
+    // See if the file is a header file
+    if(std::find( headerExts.begin(), headerExts.end(), m_SourceExtension ) == headerExts.end())
       m_HeaderFileOnly = false;
+    else
+      m_HeaderFileOnly = true;
     m_FullPath = hname;
     return;
     }