Revert "clang-cl: Hook up /Za to prevent adding oldnames.lib dependency"

This reverts commit r187991 and adjusts the comment.  /Za is much more
involved, and we don't want to give anyone the impression we actually
support it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187998 91177308-0d34-0410-b5e6-96231b3b80d8
Fix alignof computation of large arrays on x86_64.

We were exposing the extra alignment given to large arrays. The new behavior
matches gcc, which is a good thing since this is a gcc extension.

Thanks to Joerg Sonnenberger for noticing it.

While at it, centralize the method description in the .h file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187999 91177308-0d34-0410-b5e6-96231b3b80d8
clang-cl: use MS C++ ABI

Differential Revision: http://llvm-reviews.chandlerc.com/D1329

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188000 91177308-0d34-0410-b5e6-96231b3b80d8