re2: convert .hgignore to .gitignore

Change-Id: I045c5953bae55261eb224a074c10303f9f081424
Reviewed-on: https://code-review.googlesource.com/1271
Reviewed-by: Russ Cox <rsc@swtch.com>
util: disable C4800 warning (bool vs int) on Windows

Change-Id: I39e0d05e7f0a64cacc04f424a2b83d811a2d67f6
Reviewed-on: https://code-review.googlesource.com/1270
Reviewed-by: Russ Cox <rsc@swtch.com>
re2: force and fix sign-compare warnings

Change-Id: I78cbe5f8f83eff131e8cf4bad873e8af9677c701
Reviewed-on: https://code-review.googlesource.com/1272
Reviewed-by: Russ Cox <rsc@swtch.com>