lib/codereview: add LGTM= line to commit messages
lib/codereview: add LGTM= line to commit messages

The R= is populated by Rietveld, so it's basically
anyone who replied to the CL. The LGTM= is meant
to record who actually signed off on the CL.

LGTM=r
R=r
CC=golang-codereviews
https://codereview.appspot.com/55390043

tv42/old-go,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,tv42/old-go