Revert "tiff: support reading gray+alpha at 8 bits"

This reverts commit b31d76e45fc3c6529dd7109e721676f3ec376d00 as it
uses an unkown pixel format.
dct-test: Move arch-specific bits into arch-specific subdirectories
mjpeg: return proper error code

Signed-off-by: Diego Biurrun <diego@biurrun.de>
Merge commit 'a9f3f5fadb57bae3f3ff0be69e56b2c6014f2513'

* commit 'a9f3f5fadb57bae3f3ff0be69e56b2c6014f2513':
  Revert "tiff: support reading gray+alpha at 8 bits"

Not merged, the pix fmt its not unknown

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '81b9bf319226fe03436c80aaa8a2c91767cab7ce'

* commit '81b9bf319226fe03436c80aaa8a2c91767cab7ce':
  dct-test: Move arch-specific bits into arch-specific subdirectories

Conflicts:
	libavcodec/dct-test.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit 'c3ec963d0d0fac2d817f7fbce2e89ed46eeba550'

* commit 'c3ec963d0d0fac2d817f7fbce2e89ed46eeba550':
  mjpeg: return proper error code

See: 2ebaadf35c9387610ca1eb7e94c171050562a77c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/dct-test: remove fixed array sizes

They are unneeded and make adding elements slightly harder as they
would need to be constantly updated

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