Add FATE tests

This adds a "fate" make target which runs the full FATE test suite.
Individual tests can be run with "make fate-$testname".

The location of the FATE test samples must be specified with the
--samples=PATH option to configure.

The tests/fate-update.sh script regenerates the references files and
test list from the online FATE database.  These are checked in since
generating them requires non-standard tools.

Originally committed as revision 22552 to svn://svn.ffmpeg.org/ffmpeg/trunk