configure: allow bulk-disabled things to be re-enabled by dependents

Originally committed as revision 19401 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1347,6 +1347,7 @@ for opt do
     --enable-?*|--disable-?*)
     eval $(echo "$opt" | sed 's/--/action=/;s/-/ option=/;s/-/_/g')
     if is_in $option $COMPONENT_LIST; then
+        test $action = disable && action=unset
         eval $action \$$(toupper ${option%s})_LIST
     elif is_in $option $CMDLINE_SELECT; then
         $action $option