Do not disable old API after upgrading gtk+.
This avoid build error due to defination missing.

Signed-off-by: Zhai Edwin <edwin.zhai@intel.com>

Index: git/configure.ac
===================================================================
--- git.orig/configure.ac	2010-12-16 10:25:24.000000000 +0800
+++ git/configure.ac	2010-12-16 10:25:58.000000000 +0800
@@ -147,7 +147,6 @@
 AS_COMPILER_FLAGS(WARNING_FLAGS,
 	"-DG_DISABLE_DEPRECATED
 	-DPANGO_DISABLE_DEPRECATED
-	-DGDK_DISABLE_DEPRECATED
 	-DGDK_PIXBUF_DISABLE_DEPRECATED
 	-DG_DISABLE_SINGLE_INCLUDES
 	-DGTK_DISABLE_SINGLE_INCLUDES