dsputil: make selectable.
vp3/x86: use full transpose for all IDCTs.

This way, the special IDCT permutations are no longer needed. Bfin code
is disabled until someone updates it. This is similar to how H264 does
it, and removes the dsputil dependency imposed by the scantable code.
hpeldsp: add half-pel functions (currently copies of dsputil).
vp3: use hpeldsp instead of dsputil for half-pel functions.

This makes vp3 independent of dsputil.
vp56: use hpeldsp instead of dsputil for half-pel functions.

This makes vp5 and vp6 independent of dsputil.
indeo3: use hpeldsp instead of dsputil for half-pel functions.

This makes indeo3 independent of dsputil.
bink: use hpeldsp instead of dsputil for half-pel functions.
interplayvideo: use hpeldsp instead of dsputil for half-pel functions.

This makes interplayvideo independent of dsputil.
mimic: use hpeldsp instead of dsputil for half-pel functions.
svq1: use hpeldsp instead of dsputil for half-pel functions.

This makes svq1 independent of dsputil.
mpegvideo: use hpeldsp instead of dsputil for half-pel functions.

This also converts vc1, since that is mpegvideo-based.
svq3: use hpeldsp instead of dsputil for half-pel functions.
snow: use hpeldsp instead of dsputil for half-pel functions.
svq1enc: use hpeldsp instead of dsputil for half-pel functions.
mjpeg: use hpeldsp instead of dsputil for half-pel functions.
Move x86 half-pel assembly from dsputil to hpeldsp.
Move ppc half-pel assembly from dsputil to hpeldsp.
Move arm half-pel assembly from dsputil to hpeldsp.
Move bfin half-pel assembly from dsputil to hpeldsp.
Move sh4 half-pel assembly from dsputil to hpeldsp.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>