Fix alignment issues in LLVM.

Adds static_asserts to ensure alignment of concatenated objects is
correct, and fixes them where they are not.

Also changes the definition of AlignOf to use constexpr, except on
MSVC, to avoid enum comparison warnings from GCC.

(There's not too much of this in llvm itself, most of the fun is in
clang).

This seems to make LLVM actually work without Bus Error on 32bit
sparc.

Differential Revision: http://reviews.llvm.org/D10271

llvm-svn: 239872