Fix a typo.
tsan: use a single background thread for memory profiler and memory flush (and later for symbolizer flush)
tsan: add a comment about magic numbers
tsan: flush symbolizer cache if not symbolized for more than 5 seconds
[msan] Add an option to disable poisoning of shadow for undef values.
[SROA] Prefix names using a custom IRBuilder inserter.

The key part of this is ensuring that name prefixes remain in a Twine
form until we get to a point where we can nuke them under NDEBUG. This
is tricky using the old APIs as they played fast and loose with Twine,
which is prone to serious error. The inserter is much cleaner as it is
actually in the call stack leading to the setName call, and so has
a good opportunity to prepend the prefix.

This matters more than you might imagine because most runs over an
alloca find a single partition, and rewrite 3 or 4 instructions
referring to it. As a consequence doing this lazily and exclusively with
Twine allows the optimizer to delete more of it and shaves another 2% to
3% off of the release build's SROA run time for PR15412. I also think
the APIs are cleaner, and the use of Twine is more reliable, so
I consider it a win-win despite the churn required to reach this state.
Hoist the definition of getTypeSizeInBits to be inlinable and in the
header.

This method is called in the hot path for *many* passes, SROA is what
caught my interest. A common pattern is that which branch of the switch
should be taken is known in the callsite and so it is a very good
candidate for inlining and simplification. Moving it into the header
allows the optimizer to fold a lot of boring, repeatitive code in
callers of this routine.

I'm seeing pretty significant speedups in parts of SROA and I suspect
other passes will see similar speedups if they end up working with type
sizes frequently. I've not seen any significant growth of the binaries
as a consequence, but let me know if you see anything suspicious here.
[ASan] Let the users to invoke `clang -fsanitize=address` to link binaries targeting the iOS simulator.
[ASan] Switch ASan to generic ThreadRegistry from sanitizer_common. Delete ASan-specific AsanThreadRegistry.
Better block comment formatting.

Summary:
1. When splitting one-line block comment, use indentation and *s.
2. Remove trailing whitespace from all lines of a comment, not only the ones being splitted.
3. Add backslashes for all lines if a comment is used insed a preprocessor directive.

Reviewers: djasper

Reviewed By: djasper

CC: cfe-commits, klimek

Differential Revision: http://llvm-reviews.chandlerc.com/D557
tsan: remove bogus CHECK
Asynchronous signal (e.g. SIGABRT) can be received with any value of in_rtl.
tsan: intercept abort() to fflush() libc streams
tsan: add flag to control symbolizer flush frequency
tsan: better reporting for races on vptr
explicitly say "ctor/dtor vs virtual call"