Disable LLDB OSX ABI plugin

Approved by:	re (blanket)
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
Regenerate after addition of WITH_LLDB

Approved by: re (blanket)