Fixed MP4Box compile and added libMXF from BBC Prject ingest

Hello Roger,

i really appricate your work. The new cross-script works smoother than ever.

i made a small fix to the mp4box-gpac area.

i also added the libMXF from the BBC Project "Ingest" to Your script as a contribution.

The new section will give you the libMXF and libMXF++ for working with AVID-Video plus two executables 
to produce AVID-Compliant Video-Files.

Please watch out, the patch inside the libMXF Routine ist loaded from my fork at github. You will need to change this to Your repository when integrating.

I have also included a Patch for libMXF and put it into your patches subdir.

Regards
Dennis Zierahn