[MPlayer-dev-eng] better mencoder error messages

[compn]

<Bertl> what is my mencoder trying to tell me when it says:
'-x264encopts is not an MEncoder option'?
<Compn> does mencoder -ovc help list x264 ?
<Bertl> Compn: nope, so the library was missing when I compiled it, yes?
<Bertl> would be nice if mplayer would complain about the -ovc x264 :)

we get this question at least every week.

mencoderrc1 -ovc xvid -nosound d:\behind_scenes_clip1.mov -o out.avi
-xvidencopts blah

returns:
-xvidencopts is not an MEncoder option

it should say:
Option ovc: Unknown suboption xvid
when xvid/x264 etc support is not compiled.

-compn