Improve the efficiency of bytecode generated for CharClass. Change-Id: Ibf00ad9575ae800eedfc1c0f0a440fae261dce53 Reviewed-on: https://code-review.googlesource.com/4040 Reviewed-by: Russ Cox <rsc@swtch.com> Reviewed-by: Paul Wankadia <junyer@google.com>