Disable AA unit test triggering type mismatch problems.

To be able to run it there, the signatures in rt.aaA and the
compiler-internal runtime declarations would have to be updated
to taking void* like in object.di.
msync -> MemoryOrder also in LDC atomics implementation.
Fix callWithStackShell() implementation on x86.

Using intrinsics, etc. instead of dropping down to naked asm
would be preferrable, but LLVM does not seem to provide any
helpers for the required functionality.