ALL: Remove trailing whitespaces

This tries to make our code a bit more compliant with our code formatting
conventions. For future use, this is the command I used:
  git ls-files "*.cpp" "*.h" | xargs sed -i -e 's/[ \t]*$//'

graphics/surface.h

@@ -189,7 +189,7 @@ struct Surface {
 
 /**
  * A deleter for Surface objects which can be used with SharedPtr.
- * 
+ *
  * This deleter assures Surface::free is called on deletion.
  */
 struct SharedPtrSurfaceDeleter {