[ms-cxxabi] Mangle in an implicit 'E' for certain types on win64

Most of the complexity of this patch is figuring out which types get the
qualifier and which don't.  If we implement __ptr32/64, then we should
check the qualifier instead of assuming all pointers are 64-bit.

This fixes PR13792.

Patch by Warren Hunt!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181825 91177308-0d34-0410-b5e6-96231b3b80d8
Fix the MSVC build broken by r181768

MSVC accepts the using decl but not the typedef.  It complains that the
typedef is ambiguous.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181826 91177308-0d34-0410-b5e6-96231b3b80d8