Manually down-integrate python JSON struct support from internal code base.
diff --git a/.gitignore b/.gitignore
index 19e5212..a2d6ca9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -58,6 +58,7 @@
 python/.tox
 python/build/
 python/google/protobuf/compiler/
+python/google/protobuf/util/
 
 src/protoc
 src/unittest_proto_middleman