Thread Safety Analysis: add new node types to thread safety TIL.
This fills in a few missing gaps in functionality.
Remove XFAIL from a number of tests that aren't expected to fail

These tests haven't been failing on darwin11 or 12 since r189610 when
pr17027 was fixed, but they've been keeping the libc++ bot red by
XPASSing since then.
Move the TargetMachine MC options to MCTargetOptions. No functional
change.
Unify command line handling of MCTargetOptions and remove extra
options and code. No functional change.
Fill in the options in the MCOptions struct directly like the other
options.