Fix two tests in Win64 ASan

Go back to intercepting kernel32!RaiseException, and only go for
ntdll!RtlRaiseException if that fails. Fixes throw_and_catch.cc test.

Work around an issue in LLVM's win64 epilogues. We end up with an
epilogue that looks like this, and it drives the Win64 unwinder crazy
until stack overflow:
        call    ill_cc!__asan_handle_no_return
        xor     eax,eax
        add     rsp,40h // epilogue starts
        pop     rbp     // CSR
        ud2             // Trap here
        ret             // Ret?
        nop     word ptr [rax+rax]
        sub     rsp,28h // Next function

Will file a PR soon.

llvm-svn: 277874