Copy stable/11@r303970 to releng/11.0 as part of the 11.0-RELEASE
cycle.

Prune svn:mergeinfo from the new branch, and rename it to RC1.

Update __FreeBSD_version.

Use the quarterly branch for the default FreeBSD.conf pkg(8) repo and
the dvd1.iso packages population.

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

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Adopt to current and other changes:
use dedicated kernel files with some local settings
use mkimg for ISO building
put images into separate directory and rename them for better consistency

Delete all GPT partitions at once. (Suggested by Andrey V. Elsukov <bu7cher@yandex.ru>)
Fix amd64 merge script.

- Add script for preparing disks in GPT/ZFS boot environment
- Add merge script for integrating amd64 slice into i386 disk image