* modules/gui/macosx/prefs.m: fixed the module selectors.
* modules/video_filter/crop.c: clarified the use of crop. someone please check, i'm not entirely sure this is correct. Actually i think we should split this up in more then one config item, for GUI preferences clarity. Something like crop-width, crop-height, crop-h-offset, crop-v-offset, or like ffmpeg has which uses left, right, top and bottom offsets.