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

Enable warnings in EFI boot code

Set WARNS if not set for EFI boot code and fix the issues highlighted by
setting it.

Most components are set to WARNS level 6 with few being left at lower
levels due to the amount of changes needed to fix at higher levels.

Error types fixed:
* Missing / invalid casts
* Missing inner structs
* Unused vars
* Missing static for internal only funcs
* Missing prototypes
* Alignment changes
* Use of uninitialised vars
* Unknown pragma (intrinsic)
* Missing types etc due to missing includes
* printf formatting types

Reviewed by: emaste (in part)
MFC after: 2 weeks
X-MFC-With: r293268
Sponsored by: Multiplay
Differential Revision: https://reviews.freebsd.org/D4839

Add the start of the efi fdt bindings. These will be used on arm and arm64.

Sponsored by: The FreeBSD Foundation