Patch for math/py-matplotlib

Without this patch, python2.7 will crash when the loop in setup.py reaches setupext.BackendGtk3Cairo().

--- setup.py.orig       2016-09-09 04:50:50.000000000 +0200
+++ setup.py    2017-08-03 17:50:19.742905000 +0200
@@ -98,7 +98,7 @@
     setupext.BackendQt5(),
     setupext.BackendQt4(),
     setupext.BackendGtk3Agg(),
-    setupext.BackendGtk3Cairo(),
+    #setupext.BackendGtk3Cairo(),
     setupext.BackendGtkAgg(),
     setupext.BackendTkAgg(),
     setupext.BackendWxAgg(),