games/opensurge: Cleanup port

• Remove double alfont build dependency
• Fold Makefile.svn_rev into Makefile
• Move ICON_SIZES into the one place it is used
• dumb-allegro is a static library having it as a run dependency makes no sense
• Add missing lib dependencies on libalure and libpng
• Remove pkg-message
• Remove pkg-deinstall (Poudriere reports that the filesystem is clean after deinstallation and it is unclear how files would be even be created in ${DATADIR} without doing curious things like running opensurge as root)
• Add USES=localbase and build with Clang
• Fix bad absolute symlink
• Mark LLD_UNSAFE because of the audio/openal-soft dependency [1]

PR: 226980 [1]