Log Message:
mencoder, mplayer, gmplayer: avoid text relocations on NetBSD/i386 8.0.

* specify --disable-sse4 to avoid non-PIE asm ops in libmpcodecs/vf_ass.c
  that cause text relocations on NetBSD/i386
* explicitly pull pkgsrc/multimedia/libass to avoid internal libass
  (which seems usually enabled by configure's autodetect)
* specify -fpic in configure for NetBSD/i386 to enable __PIC__ blocks
  in some sources
* while here, use -mtune rather than -mcpu for not only gcc4 but
  also 5.x and later

Bump PKGREVISIONs.  Ok'ed by wiz@ in PR pkg/53319.