Updating for LLVM 3.3, plus internal changes.

Internal changes include:

    - Cleanup and simplyfing of the build/install. We now need only
      three patches (two for clang, one for libc++abi).

    - Switching to use LLVM's cmake support. This allows to build the
      stages separately without overwriting each other.

    - Linkining libcxxrt statically into libc++; it's also no longer
      installed.

    - LLVM/clang are now compiled without assertions. However, by
      default, a 3rd stage will compile another LLVM (not clang) with
      assertions and install that.

    - Support for lldb added but not activated yet as it leads to
      compile errors.

Not tested on Mac OS yet (i.e., libc++abi is untested).
Compile LLVM/clang with RTTI.
Adding an internal option to build a debug version of LLVM.
Adding a patch fixing a bug in LLVM 3.3.
Support for LLVM 3.3 on MacOS.
Merge branch 'llvm33'
Merge remote-tracking branch 'origin'