Thrift: Merging external patch.

Summary:
Merging a patch from Andy Lutomirsky.
- Allow fields to be marked "required" or "optional" (only affects C++).
- Thrift structs now have operator ==.

Reviewed By: mcslee

Test Plan: test/OptionalRequiredTest.cpp

Revert Plan: ok


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665202 13f79535-47bb-0310-9956-ffa450edef68
8 files changed