[Sema] Don't permit dependent alignments on non-dependent typedef-names

A dependent alignment attribute (like __attribute__((aligned(...))) or
__declspec(align(...))) on a non-dependent typedef or using declaration
poses a considerable challenge: the type is _not_ dependent, the size
_may_ be dependent if the type is used as an array type, the alignment
_is_ dependent.

It is reasonable for a compiler to be able to query the size and
alignment of a complete type.  Let's help that become an invariant.

This fixes PR22042.

Differential Revision: http://reviews.llvm.org/D8693

llvm-svn: 234280