multimedia/libx264: Merry Modernized Port Christmas

• Update COMMENT (library only)
• Add LICENSE_FILE
• Use pathfix for pkgconfig
• Remove unecessary WRKSRC override
• Use OPTIONS helpers
• Restore PGO option to OPTIONS_DEFINE
• Don't disable CLI so PGO can run. Remove it in post-install:
• Whitespace alignment
• Sort OPTIONS
• Remove -fstack-protector conditional (framework handles this now)
• Strip shared library