Make the Ruby generator use non-hardcoded namespaces.

Make the Ruby generator use non-hardcoded namespaces.

- Make the Ruby generator use program->get_namespace("ruby")
  instead of program->get_ruby_namespace()
- Eliminate the explicit "ruby_namespace" in t_program.
- Deprecate the ruby_namespace token.
- Update example .thrift files and syntax files.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665620 13f79535-47bb-0310-9956-ffa450edef68