re2: rename DISALLOW_EVIL_CONSTRUCTORS to DISALLOW_COPY_AND_ASSIGN

Political correctness for the win.

Change-Id: I3b3e5f7a565cb115c667386da7a94b5abcc0093d
Reviewed-on: https://code-review.googlesource.com/1590
Reviewed-by: Russ Cox <rsc@swtch.com>