[network-manager-pptp] build: set GDK_VERSION_MIN_REQUIRED, to avoid deprecation warnings

[Dan Winship <danw src gnome org>]

commit a0eca5e559b6947df76c86daeab9d4b6b51bcff1
Author: Dan Winship <danw gnome org>
Date:   Fri Nov 2 08:25:06 2012 -0400

    build: set GDK_VERSION_MIN_REQUIRED, to avoid deprecation warnings
    
    https://bugzilla.gnome.org/show_bug.cgi?id=679130

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index abe0528..095e032 100644
--- a/configure.ac
+++ b/configure.ac
@@ -94,6 +94,7 @@ if test x"$with_gnome" != xno; then
 	       *) AC_MSG_ERROR(unknown GTK+ version $with_gtkver!)
 	          ;;
 	esac
+	GTK_CFLAGS="$GTK_CFLAGS -DGDK_VERSION_MIN_REQUIRED=GDK_VERSION_3_0"
 	AC_SUBST(GTK_CFLAGS)
 	AC_SUBST(GTK_LIBS)