Implement AES-GCM in tlslite.

This adds controls to the C++ test server but doesn't use them yet. Also
ensure that tlslite never selects a 1.2 cipher suite when negotiating an
older version.

BUG=450733

Review URL: https://codereview.chromium.org/875683002

Cr-Original-Commit-Position: refs/heads/master@{#313809}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a526e23bc6fe686468b00b62d620567baf85c916
14 files changed