With this change, the output is checked immediately after each test
has run.  This means commands like "make regtest-mpeg2" can now be
used to run a single test and get meaningful results.

By default, make will abort if any test fails.  To run all tests
regardless, use make -k.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@21254 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b