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

Fix libproc on architectures that don't need the program counter to be
adjusted. This seems to be the case on all non-x86 architectures libproc
supports.

Reviewed by: kib
Obtained from: ABT Systems Ltd
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D3465

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

If the traced process stops because it received a signal, libproc needs
to ensure that the signal is forwarded when proc_continue() is called.

MFC after: 3 weeks

Modify the libproc breakpoint add/remove functions to stop the target
process if it has not already been stopped, since this is required for
ptrace(2) to work.

libdtrace does not seem to stop target processes before trying to remove
their breakpoints, so we were previously failing to remove the breakpoint
on r_debug_state() in rtld. This was causing processes to die with SIGTRAP
if they called dlopen(3) after dtrace(1) had detached.

Reported by: symbolics@gmx.com
Reviewed by: rpaulo
MFC after: 1 month

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

Several fixes for libproc:
o return the correct status in proc_wstatus()
o proc_read takes a void *
o correctly allocate the objs structure array

Sponsored by: The FreeBSD Foundation

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