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

Include machine/acle-compat.h in cdefs.h on arm if the compiler doesn't
have ACLE support built in. The ACLE (ARM C Language Extensions) defines
a set of standardized symbols which indicate the architecture version and
features available. ACLE support is built in to modern compilers (both
clang and gcc), but absent from gcc prior to 4.4.

ARM (the company) provides the acle-compat.h header file to define the
right symbols for older versions of gcc. Basically, acle-compat.h does
for arm about the same thing cdefs.h does for freebsd: defines
standardized macros that work no matter which compiler you use. If ARM
hadn't provided this file we would have ended up with a big #ifdef __arm__
section in cdefs.h with our own compatibility shims.

Remove #include <machine/acle-compat.h> from the zillion other places (an
ever-growing list) that it appears. Since style(9) requires sys/types.h
or sys/param.h early in the include list, and both of those lead to
including cdefs.h, only a couple special cases still need to include
acle-compat.h directly.

Loves it: imp

Remove redundant __ARM_ARCH >= 6 check in armv6 specific files.

Better handling of userland sysarch() requests to flush icache.

On armv6, cache maintenance can trigger page faults. Add handling so that
these turn into SIGSEGV that kills the process rather than panics that kill
the kernel.

Differential Revision: https://reviews.freebsd.org/D2035
Submitted by: Michal Meloun <meloun@miracle.cz>

Remove trailing whitespace from sys/arm/arm

Fix a paste-o.

Submitted by: Michal Meloun <meloun@miracle.cz>

Add armv6 implementations of these cache operations to avoid duplicating
the #ifdef stuff at multiple points the functions are called from. Also
rework the armv7 implementations so that the invalidate operations work
from outermost to innermost cache level, and the writeback works from
inner to outer levels.

Update comments (r4 is not used anywhere), use non-profiling entry macros.

Add cache maintenance functions which will be used by startup code to
initially set up the MMU. Some day they may also be useful as part of
suspend/resume handling, when we get better at power management.

Submitted by: Svatopluk Kraus <onwahe@gmail.com>,
Michal Meloun <meloun@miracle.cz