Fix http authentication.

Add parenthesis around "MD5" in the request string as required by
RFC 2069.

Fixes ticket #3417.

Reported and tested by Haarman
Analyzed-by: Eugen-Andrei Gavriloaie
avcodec/mjpegdec: Print human readable string for APPx

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/mjpegdec: parse adobe_transform

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/mjpegdec: Print error in case of CMYK

Also fail if AV_EF_EXPLODE is set.
We do not fail by default, but rather return some image as it may be usefull to the
end user to see what is on the image, for example text could be read quite fine and
objects recognized.

Possibly fixes Ticket3424

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