MFC r314651,r318439,r318440:

r314651:

sys/modules: normalize .CURDIR-relative paths to SRCTOP

This simplifies make output/logic

Tested with: `cd sys/modules; make ALL_MODULES=` on amd64

r318439:

Normalize .PATH on SRCTOP

This will help Jenkins dedupe 9 warnings between the static build and
the module build of ipsec(4).

Missed in SRCTOP conversion in r314651.

MFC with: r314651

r318440:

Normalize SYSDIR on SRCTOP instead of .CURDIR

This is being done to simplify pathing for CFLAGS and source files.

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

Following the repo-copy from src/sys/modules/mac_none/Makefile,
I neglected to update the filenames/etc in mac_stub. Do so now.

Forced commit to reflect repo-copy of:

modules/mac_none/Makefile -> modules/mac_stub/Makefile
security/mac_none/mac_none.c -> security/mac_stub/mac_stub.c

mac_none will become a null policy, and mac_stub will be the stub
policy from here on out.

Thanks Joe!

opt_mac.h is no longer required for any of these modules, remove from
the dependencies.

Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories

Introduce support for Mandatory Access Control and extensible
kernel access control.

Hook up various policy modules to the kernel build.

Note that a number of these modules require futher entry point commits
in the remainder of the kernel to become fully functional, but enough
of the pieces are in place to allow experimentation.

Note also that it would be desirable to not build the mac_*.ko modules
if 'options MAC' is not defined in the kernel configuration, because
the resulting modules are not useful without the kernel option. There
doesn't appear to be precedent for a way to do this -- for example,
we allow ipfw.ko to be built even if 'options NETINET' isn't defined.
Suggests welcomed on the "best" way to do this.

Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs