Add full support for MSVCRT 2013+ to druntime
Fix code generation for exceptions on Win64 and implement exception chaining.

This also reverts d12cc013df9d because this is a code generation issue.
Fix Win64 ABI wrt. passing structs > 64 bit
Merge pull request #756 from kinke/abi

Fix Win64 ABI wrt. passing structs > 64 bit
Win64 ABI hotfix
Merge pull request #757 from kinke/abifix

Win64 ABI hotfix
Fix compile error with LLVM 3.6.

The llvm::Linker class now uses diagnostic messages.
Revert "Fix compile error with LLVM 3.6."

This reverts commit cc829485cc70dd74699f315534ae1634a75e78a5.
Merge of missing changes for 2.066.1.

Merge up to 0588458.
Allow overriding of header files.

This is the same behavior as DMD.