[CodeGen] Collect information about sizes of accesses and access types for TBAA

The information about access and type sizes is necessary for
producing TBAA metadata in the new size-aware format. With this
patch, D39955 and D39956 in place we should be able to change
CodeGenTBAA::createScalarTypeNode() and
CodeGenTBAA::getBaseTypeInfo() to generate metadata in the new
format under the -new-struct-path-tbaa command-line option. For
now, this new information remains unused.

Differential Revision: https://reviews.llvm.org/D40176

llvm-svn: 319012