Add -fno-common to DLCFLAGS on Darwin

Submitted upstream, but upstream only applied it for PowerPC. Since this
doesn't break anything and only improves performance, add the flag
unconditionally.

Index: config/get_dlcflags
===================================================================
--- a/config/get_dlcflags	(revision 12594)
+++ b/config/get_dlcflags	(working copy)
@@ -2,10 +2,7 @@
 if test -n "$__gnuc__"; then
   case $osname in
     cygwin|mingw) DLCFLAGS=;;
-    darwin) DLCFLAGS=-fPIC
-      case $arch in
-        ppc|ppc64) DLCFLAGS="$DLCFLAGS -fno-common"
-      esac;;
+    darwin) DLCFLAGS="-fPIC -fno-common";;
     *) DLCFLAGS=-fPIC;;
   esac
 else #assume native compiler