allow spaces in source and build directory names

out of tree builds from a source dir with spaces is impossible
due to how make handles vpath

Originally committed as revision 6938 to svn://svn.ffmpeg.org/ffmpeg/trunk

tests/server-regression.sh

@@ -39,7 +39,7 @@ sleep 2
 )
 kill $FFSERVER_PID
 wait > /dev/null 2>&1
-if $diff_cmd data/ffserver.regression $1 ; then
+if $diff_cmd data/ffserver.regression "$1" ; then
     echo
     echo Server regression test succeeded.
     exit 0