- Copy stable/10@285827 to releng/10.2 in preparation for 10.2-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.2.
- Update default pkg(8) configuration to use the quarterly branch.[1]

Discussed with: re, portmgr [1]
Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r271931:

Add a few missing llvm/clang patches, update the other ones to be able
to apply with the same patch options onto a fresh upstream llvm/clang
3.4.1 checkout, and use approximately the same header tempate for them.

Add a few missing llvm/clang patches, update the other ones to be able
to apply with the same patch options onto a fresh upstream llvm/clang
3.4.1 checkout, and use approximately the same header tempate for them.

MFC after: 3 days