[ASTImporter] import macro source locations

Summary: Implement full import of macro expansion info with spelling and expansion locations.

Reviewers: a.sidorin, klimek, martong, balazske, xazax.hun

Reviewed By: martong

Subscribers: thakis, xazax.hun, balazske, rnkovacs, cfe-commits

Differential Revision: https://reviews.llvm.org/D47698

llvm-svn: 336269