regtest: suppress console output from tests
This disables all console output from the *-regression.sh scripts bydefault. If the V environment variable is set to 1, ffmpeg commandsare printed before being run. If V is greater than 1, ffmpeg outputgoes to the console, otherwise stderr is redirected to a file....
Split codec-regression.sh, and create the lavf-regression.sh script.
Originally committed as revision 20365 to svn://svn.ffmpeg.org/ffmpeg/trunk