Properly compute the alignment of typedefs that make use of the

Properly compute the alignment of typedefs that make use of the
"aligned" attribute. Previously, we were skipping over these
attributes when we jumped directly to the canonical type. Now,
ASTContext::getTypeInfo walks through typedefs and other
"non-canonical" types manually, looking for "aligned" attributes on
typedefs.

As part of this change, I moved the GNU-specific logic (such as
determining the alignment of void or of a function pointer) out of the
expression evaluator and into ASTContext::getTypeInfo.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@70497 91177308-0d34-0410-b5e6-96231b3b80d8