Merge remote-tracking branch 'upstream/master' into hardened/current/aout

Conflicts:
	sys/conf/options
Experimentally remove support for the a.out image activator in the
kernel.
github-issue: #45

Note: Removing a.out support also removes the gzip image activator.
The gzip image activator relies on a.out.
Remove some a.out compatibility code.
github-issue: #45
Merge remote-tracking branch 'origin/hardened/current/master' into hardened/current/aout

Conflicts:
	sys/conf/options
	sys/kern/imgact_aout.c
Merge remote-tracking branch 'origin/hardened/current/unstable' into hardened/current/aout