[MPlayer-DOCS] Undocuments -lavcopts and -lavfopts

[Oded Shimon]

Was going over old cvslog, saw Michael added some new options quite a while 
ago:

-lavcopts vglobal
   from what i understand, puts manditory headers at begginning of file 
   instead of at every keyframe (like mpeg-4 quant tables), ask Michael for 
   more details...

-lavfopts muxrate
-lavfopts packetsize
-lavfopts preload
-lavfopts delay
   ???

- ods15