[index] C++: Improve handling of typedefs as base names in C++ class declarations

Report the typedef as reference, and desugar it to report the underlying class as an
implicit 'base' reference.
Reporting the underlying base class for 'base' relations matches the ObjC handling and
leads to a simpler model.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@296975 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed