Make code portable, output to core/Support

- Moved the php script to /build/libraries (same as short-tags-remover is now)
- Added a parameter to the php script that takes the DIR_BASE as set in the grunt configuration
- Called the php script explicitly with php (so that the task can run under Windows too and we can enable short tags)
- Resulting file is now saved to core/Support
- Correctly handle async task execution