MFC r349886: linuxcommon: add module version

MFC r340181, r340185:

On amd64 both Linux compat modules, linux.ko and linux64.ko, provide
linux_ioctl_(un)register_handler that allows other driver modules to
register ioctl handlers. The ioctl syscall implementation in each Linux
compat module iterates over the list of handlers and forwards the call to
the appropriate driver. Because the registration functions have the same
name in each module it is not possible for a driver to support both 32 and
64 bit linux compatibility.

Move the list of ioctl handlers to linux_common.ko so it is shared by
both Linux modules and all drivers receive both 32 and 64 bit ioctl calls
with one registration. These ioctl handlers normally forward the call
to the FreeBSD ioctl handler which can handle both 32 and 64 bit.

Keep the special COMPAT_LINUX32 ioctl handlers in linux.ko in a separate
list for now and let the ioctl syscall iterate over that list first.
Later, COMPAT_LINUX32 support can be added to the 64 bit ioctl handlers
via a runtime check for ILP32 like is done for COMPAT_FREEBSD32 and then
this separate list would disappear again. That is a much bigger effort
however and this commit is meant to be MFCable.

This enables linux64 support in x11/nvidia-driver*.

PR: 206711
Reviewed by: kib

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

Move FEATURE macros for v4l and v4l2 to the common module.

Differential Revision: https://reviews.freebsd.org/D1075
Reviewed by: emaste

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