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

Add vm_set_register() and vm_set_desc() callbacks. These callbacks
translate directly into calls to their namesake API functions in
libvmmapi.

It is an improvement over the existing setreg(), setmsr(), setcr()
setgdt() and exec() callbacks in that the new additions give full
control and don't assume we're booting FreeBSD, like exec() and
don't assume one only wants to set the value of RSP, like setreg().

Add a callback function to userboot.so to fetch a list of environment
variables and pass them to the kernel.

Reviewed by: dfr

Replace all references to loader_callbacks_v1 with loader_callbacks.

Suggested by: grehan@

Bump USERBOOT_VERSION.

Requested by: dfr

Introduce new API to work with disks from the loader's drivers.
It uses new API from the part.c to work with partition tables.

Update userboot's disk driver to use new API. Note that struct
loader_callbacks_v1 has changed.

Add a version of the FreeBSD bootloader which can run in userland, packaged
as a shared library. This is intended to be used by BHyVe to load FreeBSD
kernels into new virtual machines.