Clean up lists of files, building libcxx / libcxxabi.
Update to current libcxx.

This doesn't work yet as it needs to be customized for use with
emscripten still.
update libcxxabi.
Remove unused makefiles.
Build libcxx and libcxxabi with C++11.
Get things working with the new libcxx / libcxxabi.
Bump version.
Get exceptions working as they were before.

This no longer uses headers from libcxxabi and
in fact uses libcxxabi a bit less than before.

This no longer lets some new C++11 stuff such as
exception_ptr work as the support for that relies
upon libcxxabi code.
remove symbol removing hack; export all malloc symbols as weak; add test for a case where symbol removing made us not merge llvm constructors properly
test fixes