- Update commit template to include 'Relnotes:' tag, to
  help re@ track release notes candidates.

Discussed with:	re
Reviewed by:	peter
MFC after:	3 days
X-MFC-To:	stable/10 only
Sponsored by:	The FreeBSD Foundation
Add new CPUTYPEs supported by Clang 3.4, i.e., AMD Steamroller (bdver3) and
Intel Silvermont (slm) processors.