multimedia: Revert removal of transcode and dependent ports

This is a partial revert of commit 60955c0a0956 which removed transcode
and ports depending on it for not building with -fno-common.

multimedia/transcode: Revert removal of port

The transcode port has been fixed to build with -fno-common by adding
1 "extern" and 3 "static" keywords to prevent some global symbols to
be defined in multiple files that are linked into one binary.

While here fix a few issues reported by "make stage-qa".

multimedia/dvdrip: remove DEPRECATED
multimedia/mkxvcd: remove DEPRECATED
multimedia/subtitleripper: remove DEPRECATED

While here add TIMESTAMP to distinfo of these ports and make portlint
and portclippy happy.

multimedia/transcode: Add TIMESTAMP to distinfo