Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r262528: Update LLDB snapshot to upstream r202189

Highlights include (upstream revs in parens):

- Improvements to the remote GDB protocol client
(r196610, r197579, r197857, r200072, and others)

- Bug fixes for big-endian targets
(r196808)

- Initial support for libdispatch (GCD) queues in the debuggee
(r197190)

- Add "step-avoid-libraries" setting
(r199943)

- IO subsystem improvements (including initial work on a curses gui)
(r200263)

- Support hardware watchpoints on FreeBSD
(r201706)

- Improved unwinding through hand-written assembly functions
(r201839)

- Handle DW_TAG_unspecified_parameters for variadic functions
(r202061)

- Fix Ctrl+C interrupting a running inferior process
(r202086, r202154)

- Various bug fixes for memory leaks, LLDB segfaults, the C++ demangler,
ELF core files, DWARF debug info, and others.

Sponsored by: DARPA, AFRL

MFC r258054: Update LLDB to upstream r194122 snapshot

Inludes minor changes relative to upstream, for compatibility with
FreeBSD's in-tree LLVM 3.3:

- Reverted LLDB r191806, restoring use of previous API.
- Reverted part of LLDB r189317, restoring previous enum names.
- Work around missing LLVM r192504, using previous registerEHFrames API
(limited functionality).
- Removed PlatformWindows header include and init/terminate calls.

Sponsored by: DARPA, AFRL

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add LLDB bmake infrastructure

This connects LLDB to the build, but it is disabled by default. Add
WITH_LLDB= to src.conf to build it.

Note that LLDB requires a C++11 compiler so is disabled on platforms
using GCC.

Approved by: re (gjb)
Sponsored by: DARPA, AFRL