multimedia/ffmpeg: update to 4.0

[jbeich]

Summary

• Add more options (some are hidden due to missing dependencies)
• Make LibreSSL use to libtls
• Drop FFSERVER after 6b35a83214f1
• Drop -mstackrealign after ea2f72a2c14c

Test Plan

• poudriere bulk -t multimedia/ffmpeg is green on 10.3 i386/amd64, 10.4 i386/amd64, 11.1 i386/amd64/armv6/aarch64, 12.0 i386/amd64/armv6/armv7/aarch64
• consumers will be tested via bug 227726

[jbeich]

• Connect LV2 to the build

[jbeich]

• Unbreak LV2=on build

[jbeich]

• Add BEIGNET option as it has a dependency

[jbeich]

Rebased after rP468598 to skip gstreamer1-libav bustage