gnu: gtk+-2: Fix failing test.

* gnu/packages/gtk.scm (gtk+-2)[source]: Add patch.
* gnu/packages/patches/gtk2-fix-failing-test.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.

Signed-off-by: Marius Bakke <mbakke@fastmail.com>

gnu/packages/patches/gtk2-fix-failing-test.patch

@@ -0,0 +1,39 @@
+From 12d8b4e8f2f9c9a7707d1d3fccba382732212e3c Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?G=C3=A1bor=20Boskovits?= <boskovits@gmail.com>
+Date: Tue, 5 Dec 2017 20:06:36 +0100
+Subject: [PATCH] Fix test failing on new GLib versions.
+
+This test fails on newer GLib version, because GLib exports a new public marshaller.
+The additional symbol making the test fail is:
+g_cclosure_marshal_BOOLEAN__BOXED_BOXED
+
+The fix makes the test ignore non-gtk related abi.
+This ensures if future marshallers are added to glib those will not pose a problem.
+
+The fix also ensures that the test still checks the gtk abi for identity, and
+that the library provides a superset of the required abi.
+
+Upstream reponse to this problem was:
+
+GLib added a new marshaller in its public API
+And the `abicheck.sh`in GTK+ 2.24 hasn't been updated because GTK+ 2.24 is in deep
+maintenance mode and very few people test it against newer versions of GLib
+
+---
+ gtk/abicheck.sh | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/gtk/abicheck.sh b/gtk/abicheck.sh
+index 0d033fb..53b7bfe 100755
+--- a/gtk/abicheck.sh
++++ b/gtk/abicheck.sh
+@@ -1,5 +1,5 @@
+ #! /bin/sh
+ 
+ cpp -DINCLUDE_VARIABLES -P -DG_OS_UNIX -DGTK_WINDOWING_X11 -DALL_FILES ${srcdir:-.}/gtk.symbols | sed -e '/^$/d' -e 's/ G_GNUC.*$//' -e 's/ PRIVATE//' | sort > expected-abi
+-nm -D -g --defined-only .libs/libgtk-x11-2.0.so | cut -d ' ' -f 3 | egrep -v '^(__bss_start|_edata|_end)' | sort > actual-abi
++nm -D -g --defined-only .libs/libgtk-x11-2.0.so | cut -d ' ' -f 3 | egrep -v '^(__bss_start|_edata|_end)' | egrep '^gtk_' | sort > actual-abi
+ diff -u expected-abi actual-abi && rm -f expected-abi actual-abi
+-- 
+2.15.0
+