Fix --enable-universalsdk and its comment line so that zsh's flag completion
works.

Thanks to Jeroen Ruigrok van der Werven for the fix.
diff --git a/configure b/configure
index a76c6fa..dfd1ef7 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 60484 .
+# From configure.in Revision: 60536 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.61 for python 2.6.
 #
@@ -1312,7 +1312,7 @@
 Optional Features:
   --disable-FEATURE       do not include FEATURE (same as --enable-FEATURE=no)
   --enable-FEATURE[=ARG]  include FEATURE [ARG=yes]
-  --enable-universalsdk[SDKDIR]
+  --enable-universalsdk[=SDKDIR]
                           Build against Mac OS X 10.4u SDK (ppc/i386)
   --enable-framework[=INSTALLDIR]
                           Build (MacOSX|Darwin) framework