Simplify vaarg support on X86_64
Add support for MIPS64.

This is the first attempt to support Linux/MIPS64.
Add some ARM eh related code.

This is a copy of the easy part of issue #489.
Merge remote-tracking branch 'alexey/testSuiteFixes' into ldc
ARM fixes for 2.065
Fix partial merged ARM EH code
Remove out of date intrinsics.

Removes the llvm.part.* intrinsics and enables llvm.umul.with.overflow.
This fixes issue #640.
Fix build on PPC64.

Add the missing `fenv_t` and `fexcept_t` types.
Fix build on Win64