configure: Don't use symlinks for creating the out of tree makefile

On some platforms (such as msys), symlinks are (poorly) emulated
by simply creating a copy of the file.

This means that when building out of tree, the build tree gets
a copy of the original makefile, which can lead to unintuitive
build errors when the original makefile gets updated later.

Instead simply create a stub makefile which includes the real
one.

Signed-off-by: Martin Storsjö <martin@martin.st>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  configure: Don't use symlinks for creating the out of tree makefile

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avformat/jacosubdec: make probing less tolerant.

Fixes a failure with probetest:
  ./tools/probetest 8192 500000
  [...]
  Failure of jacosub probing code with score=51 type=1 p=CAB size=16

Random data was:
  00000000  40 37 40 30 93 01 48 e0 09 96 10 90 78 0f 0c 10 @7@0..H.....x...
swscale: add nv12/nv21->yuv420 converter

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
swscale: fix used stride in planarToNv12Wrapper()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
swscale/x86/rgb2rgb: extend framework to also include AVX

This does not yet include any actual AVX code

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
swscale/x86/rgb2rgb: change cpu optim identifiers to lower case

This makes the code more similar to the other optims and allows us
to use the same macros to build function names

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
swscale/x86/rgb2rgb_template: add mmx/sse2/avx optimized deinterleaveBytes

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