Reduce reliance on sys/sysproto.h pollution

Add sys/errno.h, sys/malloc.h, sys/queue.h, and vm/uma.h as needed.

sys/sysproto.h currently includes sys/acl.h which currently includes
sys/param.h, sys/queue.h, and vm/uma.h which in turn bring in
sys/errno.h sys/malloc.h.

Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D44465

sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Add membarrier(2)

This is an attempt at clean-room implementation of the Linux'
membarrier(2) syscall. For documentation, you would need to read
both membarrier(2) Linux man page, the comments in Linux
kernel/sched/membarrier.c implementation and possibly look at
actual uses.

Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D32360