multimedia/mplayer2: modernize options

• Expose A52, ENCA, DVDREAD, DVDNAV, RTCPU as options
• Hide WIN32 option for non-i386 architectures
• Drop no longer supported OSVERSION range
• Drop DEBUG and PACKAGE_BUILDING hacks
• Convert to option helpers
• Sort options

PR: 202404
Submitted by: Carlos J Puga Medina <cpm@fbsd.es> (maintainer)