Starting to prepare for LLVM 3.5 (as of current git).

Also preparing to bring lldb building back.

Includes a feature patch to enable the stackmap intrinsic on ELF.
More work for LLVM 3.5

Now using cmake for building libc++abi.

README still out of date. Darwin untested.
Latest libcxx can now link to in-tree libc++abi directly.

Also removing the stackmap patch, as it has been commited to trunk.
Adding stackmaps-for-ELF patch from upstream.

LLVM git revision ec9de4677ac61
Fixes for Darwin.

Includes mechanism to cherry-pick existing commits.
Cleanup.

Removing code that's no longer needed.
Removing support for libcxxrt.

libc++abi now seems to work fine on both Linux and Darwin, and it's
(mostly) integrated into the LLVM build system.
Fixing typo.

Note: doesn't compile on Linux anymore right now. Sigh.

/usr/bin/ld:
../../lib/libLLVMAArch64CodeGen.a(AArch64AsmPrinter.cpp.o): relocation
R_X86_64_32S against `.text' can not be used when making a shared
object; recompile with -fPIC
Fix for Linux.

This turns on building shared libraries.
Disabling stage 3 for now.

Now that we're building shared libraries, this doesn't quite work
anymore.
Linux fix now that we are compiling shared libraries.
Removing stage 3 and adding options to select build mode and assertions.
Hardcoding current libcxxabi.
Switching Darwin to shared libraries as well.
Updating README.
Merge branch 'llvm35'