More work porting to PPC. libs/winloader is disabled on PPC - I doubt this can be...

More work porting to PPC. libs/winloader is disabled on PPC - I doubt this can be made to work.

Original commit message from CVS:
More work porting to PPC.
libs/winloader is disabled on PPC - I doubt this can be made to work.
libs/videoscale and libs/idct are also disabled - they should be fixable
though.

Sorted out most of the plugins - avi is disabled for now on PPC;
can be worked on later if there's any chance of getting it to work.

Also provide an automake conditional for compiling vorbis, based on a
configure test for the needed libraries: currently the test isn't
implemented and defaults to "no" so you'll have to fiddle it to compile
vorbis.  I shall get hold of vorbis and implement an appropriate test some
other time (if noone else beats me to it).