macosx: minor code cleanup
extras/ios: don't use small contribs anymore
ffmpeg/libav: allow the use of 'thumb' if we don't specify 'small'
postproc: allow the use of 'thumb' if we don't specify 'small'
quartztext: fix relative font size handling
extras/package: compile quartztext module for iOS
extras/tools: disable contrib compilation of gpg-error, gcrypt and lua since we don't use it for now