MFC SVN r329188,329334,329353,329914,329995-329996: DTrace Enhancements

r329188: Use tabs in io.d, fix alignment issues, remove extra newlines
r329334: Add errno definitions to /usr/lib/dtrace/errno.d
r329353: Add inline to errno.d for translating int to string
r329914: Updates and enhancements to io.d to aid DTrace scripting
r329995: Updates and enhancements to signal.d to aid DTrace scripting
r329996: Consistent casing for fallback SIGCHLD (s/Unknown/unknown/)

MFC SVN r330559-330560,330672,332865-332867,333513-333519: dwatch(1)

r330559: Introduce dwatch(1) as a tool for making DTrace more useful
r330560: Bump dwatch(1) internal version from 1.0-beta-91 to 1.0
r330672: Fix display of wrong pid from dtrace_sched(4)
r332865: Add `-dev' option to aid debugging of profiles
r332866: Add profile for send(2)/recv(2) syscalls
r332867: Remove the line used to demonstrate `-dev' option
r333513: Bugfix, usage displayed with `-1Q'
r333514: Separate default values so `-[BK] num' don't affect usage
r333515: Simplify info message test
r333516: Export ARGV to profiles loaded via load_profile()
r333517: Allow `-E code' to override profile EVENT_DETAILS
r333518: Expose process for ip/tcp/udp
r333519: Refactor sendrecv profile

Reviewed by: markj, gnn, bdrewery (head; earlier version)
Approved by: re (gjb)
Relnotes: yes
Sponsored by: Smule, Inc.
Differential Revision: https://reviews.freebsd.org/D15418

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

libdtrace: add support for lazyload mode.

Passing "-x lazyload" to dtrace -G during compilation causes dtrace(1) to
not link drti.o into the output object file, so the USDT probes are not created
during process startup. Instead, dtrace(1) will automatically discover and
create probes on the process' behalf when attaching.

Differential Revision: https://reviews.freebsd.org/D2203
Reviewed by: rpaulo
MFC after: 1 month

Hook up support for userland CTF support in DTrace. This required some
modifications to libproc to support fetching the CTF info for a given file.

With this change, dtrace(1) is able to resolve type info for function and
USDT probe arguments, and function return values. In particular, the args[n]
syntax should now work for referencing arguments of userland probes,
provided that the requisite CTF info is available.

The uctf tests pass if the test programs are compiled with CTF info. The
current infrastructure around the DTrace test suite doesn't support this
yet.

Differential Revision: https://reviews.freebsd.org/D891
MFC after: 1 month
Relnotes: yes
Sponsored by: EMC / Isilon Storage Division

Make DTrace stuff compile with C99 standard.

Add stubs for CTF functions which are not yet implemented.

MFC after: 2 weeks

Remove a duplicate definition.

MFC after: 3 days

Add libdtrace support for tracing userland programs.

Summary of changes:
* Implement a compatibility shim between Solaris libproc and our
libproc and remove several ifdefs because of this.
* Port the drti to FreeBSD.
* Implement the missing DOODAD sections
* Link with libproc and librtld_db
* Support for ustack, jstack and uregs (by sson@)
* Misc bugfixing

When writing the SUWN_dof section, we had to resort to building the ELF
file layout by "hand". This is the job of libelf, but our libelf doesn't
support this yet. When libelf is fixed, we can remove the code under
#ifdef BROKEN_LIBELF.

Sponsored by: The FreeBSD Foundation