Improve color management for JPEG files

A while ago I wrote two patches for EOG 2.30.2 (for Debian Squeeze at the time), they never made it upstream because EOG 2.32 was already released and the GNOME team moved onto 3.x...

These patches may be of interest to you, though keep in mind I no longer use GNOME 2.x or MATE, so I have NOT tested these patches.

The first patch fixes poor behavior on EOG/EOM's part when reading a JPEG file which has no (or very limited) EXIF information, where color management gets disabled. Except that it should never be disabled, but sRGB parameters should be assumed when information is missing.

The second patch fixes poor behavior on EOG/OEM's part when reading AdobeRGB encoded JPEG files (typically straight from higher end cameras, the nasty part is that these camera's don't embed a proper AdobeRGB ICC profile into the JPEG :(), so EOG/EOM has to recognize from EXIF it's AdobeRGB encoded, which it already detects, but instead of disabling color management it should use an internal copy of AdobeRGB to decode the image data.

Again I'd like to emphasize I wrote and tested these patches for EOG 2.30 in a slightly modified form. As submitted here the patches are untested, but they should be sound.