Fix gcc detection: Not all gcc versions have "(GCC)" in the version string.

Originally committed as revision 17522 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1356,7 +1356,7 @@ EOF
 fi
 rm $TMPSH
 
-if   $cc --version 2>/dev/null | grep -q '(GCC)'; then
+if   $cc --version 2>/dev/null | grep -qi gcc; then
     cc_type=gcc
 elif $cc --version 2>/dev/null | grep -q Intel; then
     cc_type=icc