multimedia/ffmpeg: update to 3.4
Notable changes:
- i386/amd64 now depend on NASM per https://git.ffmpeg.org/gitweb/ffmpeg.git/commitdiff/4f9297ac3b39
- NETCDF is now MYSOFA but the dependency doesn't exist in ports yet
- SCHROEDINGER is gone per https://git.ffmpeg.org/gitweb/ffmpeg.git/commitdiff/220b24c7c9
- DRM, LIBRSVG2, LIBXML2 are new options
- ABI isn't completely compatible: some structs have changed
Minor cleanup:
- Don't pass --disable-{in,out}dev when it's already blocked by disabled dependency
- Drop redundant "Enable" from option descriptions
- Switch CDIO_DESC to use Mk/bsd.options.desc.mk
Changes: https://git.ffmpeg.org/gitweb/ffmpeg.git/blob/n3.4:/Changelog
ABI: https://abi-laboratory.pro/tracker/timeline/ffmpeg/
PR: 223057
Exp-run by: antoine