In vout_CreatePicture() replace i_repeat_first_field by the more useful
  i_nb_fields
* modules/gui/macosx/intf.m: Fixed a warning
* modules/codec/libmpeg2.c include/vout_synchro.h src/video_output/vout_synchro.c:
  Re-added support for slice-I streams, plus miscellaneous tweakings