--extra-cflags and --extra-ldflags clobbers previous options. This

patch will add instead of clobber.
patch by (Roine Gustafsson <roine users.sourceforge net)

Originally committed as revision 3807 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -370,9 +370,9 @@ for opt do
   ;;
   --make=*) make=`echo $opt | cut -d '=' -f 2`
   ;;
-  --extra-cflags=*) CFLAGS="${opt#--extra-cflags=}"
+  --extra-cflags=*) CFLAGS="$CFLAGS ${opt#--extra-cflags=}"
   ;;
-  --extra-ldflags=*) LDFLAGS=${opt#--extra-ldflags=}
+  --extra-ldflags=*) LDFLAGS="$LDFLAGS ${opt#--extra-ldflags=}"
   ;;
   --extra-libs=*) extralibs=${opt#--extra-libs=}
   ;;