Squashed 'sources/cxx-stl/llvm-libc++abi/libcxxabi/' changes from 0fd027b..2b683fb

2b683fb Let libc++abi compile with gcc.

git-subtree-dir: sources/cxx-stl/llvm-libc++abi/libcxxabi
git-subtree-split: 2b683fb0b15d8a56537640c5c9d8073da55e5871
Merge commit 'b7e718ef59213cef3c7c19047d8ef1a892c4f6c4' into upstream-llvm
Merge branch 'upstream-llvm' into upstream-llvm-ndkpatched
Pull in upstream libc++abi change for cxa_demangle.cpp, fix conflict.

Change-Id: Iacd84d9ee2cfbe06e8eb723f46477a6da53c77f9
Allow libc++ to be built on systems without POSIX threads
Locale fixes for when there are no xlocale extesions
Hack up support for monotonic clock when the libc doesn't provide one
Remove include that's not necessary yet.
Merge pull request #92 from awong-dev/enable_single_threaded_libcxx

Enable single threaded libcxx
Merge pull request #93 from awong-dev/enable_libcxx_on_newlib

Enable libcxx on newlib
Merge pull request #94 from awong-dev/fix_monotonic_clock

Fix monotonic clock
Clean up ifdef logic for finding the exception table via libdl versus static linker resolution.

Change-Id: I05800e26d6e15f4cc1c3a35e6bf97360ba72f9e0