Try to fix a periodic windows build failure due to broken rwildcard macro
Start building a multithreaded LLVM
Upgrade LLVM
Fix build issues once LLVM has been upgraded

* LLVM now has a C interface to LLVMBuildAtomicRMW
* The exception handling support for the JIT seems to have been dropped
* Various interfaces have been added or headers have changed
Fix setting the fixed stack segment attribute on LLVM functions

At the same time create a more robust wrapper to try to prevent this type of
issue from cropping up in the future.