configure: Separate MinGW32 and MinGW64 libc handling
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  configure: Separate MinGW32 and MinGW64 libc handling

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/ffv1: support adjusting the g vs r + b coefficient in the RCT

about 1% better compression

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/ffv1enc: support forcing experimental 1.4 version

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