- Copy stable/10@296371 to releng/10.3 in preparation for 10.3-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.3.
- Update default pkg(8) configuration to use the quarterly branch.

Approved by: re (implicit)

MFC r271875, r272046, r272049, r272056
-> Reference the test case "packs" to fix warnings
-> Delete mentions to removed manpages
-> Minor fixes to docs

Approved by: re (gjb)

Update atf to 0.18 and remove the code of the deprecated tools.

This is a MFC into stable/10 of:
- r258286 Update notes for imports of atf.
- r258289 MFV: Import atf-0.18.
- r258290 Drop all ATF tools code.

This is "make tinderbox" clean as run on ref10-amd64 with the default
WITHOUT_TESTS option. A "make buildworld" with WITH_TESTS set now works
as well.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add ATF update instructions and file exclude list.

Submitted by: Garrett Cooper <yanegomi@gmail.com>