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/conformance/conformance_objc.m b/conformance/conformance_objc.m
index 1124bfe..ef037f8 100644
--- a/conformance/conformance_objc.m
+++ b/conformance/conformance_objc.m
@@ -31,6 +31,7 @@
 #import <Foundation/Foundation.h>
 
 #import "Conformance.pbobjc.h"
+#import "google/protobuf/TestMessagesProto3.pbobjc.h"
 
 static void Die(NSString *format, ...) __dead2;