Factored Conformance and Benchmark test messages into shared test schema. (#1971)

* Factored Conformance test messages into shared test schema.

* Updated benchmarks to use new proto3 message locations.

* Fixed include path.

* Conformance: fixed include of Python test messages.

* Make maven in Rakefile use --batch-mode.

* Revert changes to benchmarks.

On second thought I think a separate schema for
CPU benchmarking makes sense.

* Try regenerating C# protos for new test protos.

* Removed benchmark messages from test proto.

* Added Jon Skeet's fixes for C#.

* Removed duplicate/old test messages C# file.

* C# fixes for test schema move.

* Fixed C# to use the correct TestAllTypes message.

* Fixes for Objective C test schema move.

* Added missing EXTRA_DIST file.
diff --git a/csharp/generate_protos.sh b/csharp/generate_protos.sh
index d979aa5..7cbcf43 100755
--- a/csharp/generate_protos.sh
+++ b/csharp/generate_protos.sh
@@ -54,6 +54,11 @@
     --csharp_opt=base_namespace=UnitTest.Issues \
     csharp/protos/unittest_issues.proto
 
+# Don't specify a base namespace at all; we just want to make sure the
+# results end up in TestProtos.
+$PROTOC -Isrc --csharp_out=csharp/src/Google.Protobuf.Test/TestProtos \
+    src/google/protobuf/test_messages_proto3.proto
+
 # AddressBook sample protos
 $PROTOC -Iexamples --csharp_out=csharp/src/AddressBook \
     examples/addressbook.proto