Fix NaN and Infinity on Win64.

Using the numerical limits (e.g. std::numeric_limits<double>::quiet_NaN()) seems not return the expected value.
This fixes issue #750.
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
Win64: don't use DMD x64 implementations of LDC_va_start and LDC_va_copy intrinsics
Do not emit variables for enum declarations.

GitHub: Fixes #762.
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.
Fix compile error with LLVM 3.6.

The llvm::Linker class now uses diagnostic messages.
Implement missing -boundscheck switch in ldmd.

This was reported in the newsgroup by Daniel N.
Merge pull request #752 from redstar/merge-2.066.1

Merge of missing changes for 2.066.1.
Merge pull request #764 from redstar/llvm36

Fix compile error with LLVM 3.6.
Merge pull request #760 from kinke/vararg

Win64: don't use DMD x64 implementations of LDC_va_start and LDC_va_copy intrinsics
Merge pull request #765 from redstar/ldmd

Implement missing -boundscheck switch in ldmd.
Changes for Win64 and PPC32/64

- Added math function using MSVC runtime
- Added PPC inline assembler for getStackTop()