Bring in WebKit revisions 139553 and 139921.

They are primarily useful for getting rid of some libstdc++-specific
includes which break the build with libc++, and also for simplifying the
code and removing a Darwin-specific code path.

r139553 by ossy@webkit.org:
  Use sync_add_and_fetch instead of gnu_cxx::exchange_and_add
  https://bugs.webkit.org/show_bug.cgi?id=106729

  After r139514 we need atomicIncrement(int64_t volatile*) for all
  platform. Now the GCC implementation of atomicIncrement() is based on
  gnu_cxx::exchange_and_add, which doesn't support int64_t type, but
  sync_add_and_fetch does.

  Reviewed by Benjamin Poulain.

r139921 by benjamin@webkit.org:
  Use GCC's implementation of atomicIncrement/Decrement on Mac
  https://bugs.webkit.org/show_bug.cgi?id=106976

  Reviewed by Filip Pizlo.

  wtf/Atomics.h: GCC and LLVM have builtin for atomic ADD and SUB:
                 sync_add_and_fetch, sync_sub_and_fetch.

  Using them let the compiler just generate the atomic operations inline
  instead of generating a function call to LibC. It also simplify the
  code a bit.

Cherry-picked from qtwebkit/0baf197 and qtwebkit/801fc96. I'm cherry-picking
both revisions together to match what was done in 0de22e80.

Change-Id: Ie5c1067980662ff04e8e36d8cf6e9459b7c46aab
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>
BlackBerry: Increased loop level around bps_get_event

This is needed, because bps_get_event can also invoke callbacks.
Deferred deletions in such a callback are not executed for instance,
because the loop level might already be at its minimum.
Backported from qtbase: f62c92b

Change-Id: I83d72d773d53b7b84ec590180f6b1131a57e0f46
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>