Explicit instantiations following specializations are no-ops and hence have
no PointOfInstantiation. That was done correctly in most cases, but for a
specialization -> instantiation decl -> instantiation definition chain, the
definition didn't realize that it was a no-op. Fix that.
Also, when printing diagnostics for these no-ops, get the diag location from
the decl name location.
Add many test cases, one of them not yet passing (but it failed the same way
before this change). Fixes http://llvm.org/pr11558 and more.
llvm-svn: 147225