Adding lib for c++ abi and unwind

libc++ is basically workable only for LTO and no exception at present.
So add compiling options: -stdlib=libc++ -flto
Sample 03 and 04 passed in LTO mode.

There are kinds of combination to build libc++.
But libc++-3.3 + libsupc++-4.2 + libgcc_eh-4.2 is the one look promising.

Two apparent issues left:
Exception is not done, both in lib and backend.
Alias ctor and dtor is not correctly generated.