Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

stand/boot1.efi: Allow modules to add env variables

Sometimes filesystem modules need to pass details of the state of the
filesystem to later stages of a boot. Provide a generic method to do
so. We'll add them after any env variables set in our config files.

Sponsored by: Netflix
Reviewed by: tsoome, kevans
Differential Revision: https://reviews.freebsd.org/D39407

Fix gcc build by removing redeclaration

Reviewed by: imp
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D20622

Break out the disk selection protocol from the rest of boot1.

Segregate the disk probing and selection protocol from the rest of the
boot loader.

Reviewed by: tsoome, bcran
Differential Revision: https://reviews.freebsd.org/D20547

Remove stray '*'

We're storing an EFI_HANDLE, not an pointer to a handle. Since
EFI_HANDLE is a void * anyway, this has little practical effect since
the conversion to / from void * and void ** is silent.

Revert preference to be an int.

While in base we use it as a boolean (of the wrong spelling), there's
at least one out of tree user that needs it to be int since priorirty
is a small int, not a 0/1. In deference to the time it's wasted me and
my team, push this up into FreeBSD for whatever short life boot1 may
have in the tree.

Teach ufs_module.c about bsd labels and probe 'a' partition.

If the check for a UFS partition at offset 0 on the disk fails, check
to see if there's a BSD disklabel at block 1 (standard) or at offset
512 (install images assume 512 sector size). If found, probe for UFS
on the 'a' partition.

This fixes UEFI booting images from a BSD labeled MBR slice when the
'a' partiton isn't at offset 0. This is a stop-gap fix since we plan
on removing boot1.efi in FreeBSD 12. We can't easily do that for 11.2,
however, hence the short MFC window.

Tested by: emaste@
MFC After: 3 days
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D15598

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix