* fixing a bug in avpicture_layout (PAL8 wasn't handled properly)
   * adding regression tests for all pix_fmt conversions
   * making libavtest part of the default testsuite


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@1855 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b