Add UFL patch

patches/ufl/0001-Give-conditional-an-ufl_id.patch

+From 8caa33075fba04cfc5bdcb47452a3c5ca400c0c5 Mon Sep 17 00:00:00 2001
+From: Dominic Kempf <dominic.kempf@iwr.uni-heidelberg.de>
+Date: Thu, 15 Dec 2016 23:30:03 +0100
+Subject: [PATCH] Give conditional an ufl_id
+
+---
+ ufl/conditional.py | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/ufl/conditional.py b/ufl/conditional.py
+index faffbb5..e48ee19 100644
+--- a/ufl/conditional.py
++++ b/ufl/conditional.py
+@@ -240,6 +240,9 @@ class Conditional(Operator):
+     def __repr__(self):
+         return "Conditional(%r, %r, %r)" % self.ufl_operands
+ 
++    def ufl_id(self):
++        return 0
++
+ 
+ #--- Specific functions higher level than a conditional ---
+ 
+-- 
+2.1.4
+