Properly support maps in Ruby protoc and another bugfix.

Previously, we supported map fields in the Ruby DSL. However, we never
connected the final link in the chain and generated `map` DSL commands
for map fields in `.proto` files. My apologies -- I had been testing
with the DSL directly so I missed this.

Also fixed a handlerdata-setup-infinite-loop when a map value field's
type is its containing message.

MIPS: remove immediate constraint within CompareAndSwap.

Add java compiled targets and several tests target into .gitignore.

Improper use of immediate constraint is slightly non-optimal with gcc/gnu-as
but may cause breakage with clang.

Add missing LIBPROTOC_EXPORT to ruby generator

Updated to latest upb and added test for JSON map operation.

add #to_ary to RepeatedField

MSVC protoc compiler fix

Support oneofs in MRI Ruby C extension.

<stdint.h> is not part of the standard, so I've added a workaround.

https://github.com/google/protobuf/issues/87

Fix illegal C++ use of reinterpret_cast<> to cast between nullptr_t and a pointer

- A golden-file test that ensures protoc produces known-valid output.
- A Ruby test that loads that golden file and ensures it actually works
  with the extension.

This split strategy allows us to test end-to-end without needing to
integrate the Ruby gem build system and the protoc build system. This is
desirable because we do not want a gem build/install to depend on
building protoc, and we do not want building protoc to depend on
building and testing the gem.

Support for maps in the MRI C Ruby extension.

Include names.h as java_names.h in the opensource tree