gvim: Fix compilation against GNOME 2.18

From: Daniel Drake <dsd@gentoo.org>

Index: vim7/src/gui_gtk.c
===================================================================
--- vim7.orig/src/gui_gtk.c
+++ vim7/src/gui_gtk.c
@@ -53,6 +53,9 @@
 # ifdef bindtextdomain
 #  undef bindtextdomain
 # endif
+# ifdef bind_textdomain_codeset
+#  undef bind_textdomain_codeset
+# endif
 # if defined(FEAT_GETTEXT) && !defined(ENABLE_NLS)
 #  define ENABLE_NLS	/* so the texts in the dialog boxes are translated */
 # endif
Index: vim7/src/gui_gtk_x11.c
===================================================================
--- vim7.orig/src/gui_gtk_x11.c
+++ vim7/src/gui_gtk_x11.c
@@ -36,6 +36,9 @@
 # ifdef bindtextdomain
 #  undef bindtextdomain
 # endif
+# ifdef bind_textdomain_codeset
+#  undef bind_textdomain_codeset
+# endif
 # if defined(FEAT_GETTEXT) && !defined(ENABLE_NLS)
 #  define ENABLE_NLS	/* so the texts in the dialog boxes are translated */
 # endif