LDC Windows exception handling

[Christian Kamm]

Don wrote:
>> Adding exception support to LLVM is probably *much* easier than
>> converting the exception support in a compiled object file.

Walter Bright wrote:
> There's no way to add it to a compiled object file. The schemes are
> completely different, and interact with the rest of the code generation.
> Might as well try to turn hamburger back into a cow.

Yes. The most sensible approach would be adding SEH support to LLVM. Neither
Tomas nor me are planning to do it though. We hope that someone who
actually develops on Windows will volunteer. 

As clang and llvm-gcc would also benefit from it, this might do well as a
Summer of Code project at LLVM. From what I hear exception support in LLVM
is due for a revamp anyway, so anyone attempting to do this would probably
get a chance to help redesign the infrastructure and be well supported by
the LLVM devs.