MFC r351408-r351410: reduce pollution from mips machine/regnum.h

r351408:
libsa: mips: use _JB_* from machine/asm.h, remove regnum dep

This brings the libsa/mips _setjmp implementation closer to parity with the
libc version.

r351409:
mips: hide regnum definitions behind _KERNEL/_WANT_MIPS_REGNUM

machine/regnum.h ends up being included by sys/procfs.h and sys/ptrace.h via
machine/reg.h. Many of the regnum definitions are too short and too generic
to be exposing to any userland application including one of these two
headers. Moreover, these actively cause build failures in googletest
(template <typename T1 ...> expanding to template <typename 9 ...>).

Hide the definitions behind _KERNEL or _WANT_MIPS_REGNUM, and patch all of
the userland consumers to define as needed.

r351410:
libsa: mips: fix typo that had slipped into the diff on local machine

MFC r309591:
Fix style bugs and remove trailing whitespace in libproc and librtld_db.

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

Add support for RISC-V ISA.

Reviewed by: andrew
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
Differential Revision: https://reviews.freebsd.org/D5040

Make libproc compilable on AArch64.

Initial version of DTrace on ARM32.

Submitted by: Howard Su based on work by Oleksandr Tymoshenko
Reviewed by: ian, andrew, rpaulo, markj

Clean up the debug printing in libproc a bit. In particular:

* Don't print any error messages to stderr unless DEBUG is defined.
* Add a DPRINTFX macro for use when errno isn't set.
* Print the error string from libelf when appropriate.

Implement DTrace for PowerPC. This includes both 32-bit and 64-bit.

There is one known issue: Some probes will display an error message along the
lines of: "Invalid address (0)"

I tested this with both a simple dtrace probe and dtruss on a few different
binaries on 32-bit. I only compiled 64-bit, did not run it, but I don't expect
problems without the modules loaded. Volunteers are welcome.

MFC after: 1 month

Make libproc compilable for MIPS

New version of libproc. Changes are:
* breakpoint setup support
* register query
* symbol to address mapping and vice-versa
* more misc utility functions based on their Solaris counterpart

Also, I've written some test cases.

Sponsored by: The FreeBSD Foundation