Teach __alignof__ to look through arrays before performing the
preferred-alignment transformations. Corrects alignof(T[]) to return
alignof(T) in all cases, as required by relevant standards.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@210609 91177308-0d34-0410-b5e6-96231b3b80d8