[clang][Index] Mark references from Constructors and Destructors to class as NameReference

Summary:
In current indexing logic we get references to class itself when we see
a constructor/destructor which is only syntactically true. Semantically
this information is not correct. This patch marks that reference as
NameReference to let clients deal with it.

Reviewers: akyrtzi, gribozavr, nathawes, benlangmuir

Reviewed By: gribozavr, nathawes

Subscribers: nathawes, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58814

llvm-svn: 355668