Produce correct version string even when not run in a Subversion working copy.

based on a patch by Ismail Dönmez ismail##@##pardus##.##org##.##tr


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@5511 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

version.sh

 #!/bin/sh
 
-svn_revision=`svn info | grep Revision | cut -d' ' -f2 || echo UNKNOWN`
+svn_revision=`svn info 2> /dev/null | grep Revision | cut -d' ' -f2`
+test $svn_revision || svn_revision=UNKNOWN
+
 NEW_REVISION="#define FFMPEG_VERSION \"SVN-r$svn_revision\""
 OLD_REVISION=`cat version.h 2> /dev/null`