authors and changelog update for swift 1.7.6

Change-Id: Iad00e51fb17c9e829bd5ba7b56a0d24253cfe8b2
version bump to 1.7.7-dev

I expect the next release to actually be 1.8, but to prevent issues
if we decide to release 1.7.7, I'm only moving the rev number.

Change-Id: Ia9e05c5f036b8fbf67972470f240e84f7595223a
Merge "version bump to 1.7.7-dev"