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

MFC r302517:

Fix a copy/paste bug introduced during X86_64 Linuxulator work.
FreeBSD support NX bit on X86_64 processors out of the box, for i386 emulation
use READ_IMPLIES_EXEC flag, introduced in r302515.

While here move common part of mmap() and mprotect() code to the files in compat/linux
to reduce code dupcliation between Linuxulator's

Approved by: re (gjb)

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

Rework signal code to allow using it by other modules, like linprocfs:

1. Linux sigset always 64 bit on all platforms. In order to move Linux
sigset code to the linux_common module define it as 64 bit int. Move
Linux sigset manipulation routines to the MI path.

2. Move Linux signal number definitions to the MI path. In general, they
are the same on all platforms except for a few signals.

3. Map Linux RT signals to the FreeBSD RT signals and hide signal conversion
tables to avoid conversion errors.

4. Emulate Linux SIGPWR signal via FreeBSD SIGRTMIN signal which is outside
of allowed on Linux signal numbers.

PR: 197216

Refund the proc emuldata struct for future use. For now move flags from
thread emuldata to proc emuldata as it was originally intended.

As we can have both 64 & 32 bit Linuxulator running any eventhandler
can be called twice for us. To prevent this move eventhandlers code
from linux_emul.c to the linux_common.ko module.

Differential Revision: https://reviews.freebsd.org/D1073

Introduce a new module linux_common.ko which is intended for the
following primary purposes:

1. Remove the dependency of linsysfs and linprocfs modules from linux.ko,
which will be architecture specific on amd64.

2. Incorporate into linux_common.ko general code for platforms on which
we'll support two Linuxulator modules (for both instruction set - 32 & 64 bit).

3. Move malloc(9) declaration to linux_common.ko, to enable getting memory
usage statistics properly.

Currently linux_common.ko incorporates a code from linux_mib.c and linux_util.c
and linprocfs, linsysfs and linux kernel modules depend on linux_common.ko.

Temporarily remove dtrace garbage from linux_mib.c and linux_util.c

Differential Revision: https://reviews.freebsd.org/D1072
In collaboration with: Vassilis Laganakos.

Reviewed by: trasz