Merge lldb trunk r300422 and resolve conflicts.

Update lldb to trunk r290819 and resolve conflicts.

Update lldb to upstream trunk r242221.

Update LLDB snapshot to upstream r216948 (git 50f7fe44)

This is approximately "LLDB 3.5" although with a little bit of skew,
and will go along with the Clang 3.5 import.

Sponsored by: DARPA, AFRL