unify include guard defines, __$FILENAME__

without the underscores these clogged up the namespace for autocompleation which was annoying.

source/blender/imbuf/intern/dds/DirectDrawSurface.h

@@ -55,8 +55,8 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 // OTHER DEALINGS IN THE SOFTWARE.
 
-#ifndef _DDS_DIRECTDRAWSURFACE_H
-#define _DDS_DIRECTDRAWSURFACE_H
+#ifndef __DIRECTDRAWSURFACE_H__
+#define __DIRECTDRAWSURFACE_H__
 
 #include <Common.h>
 #include <Stream.h>
@@ -198,4 +198,4 @@ void mem_read(Stream & mem, DDSCaps & caps);
 void mem_read(Stream & mem, DDSHeader & header);
 void mem_read(Stream & mem, DDSHeader10 & header);
 
-#endif // _DDS_DIRECTDRAWSURFACE_H
+#endif // __DIRECTDRAWSURFACE_H__