Implement C++ [basic.lookup.classref]p3, which states how the type

Implement C++ [basic.lookup.classref]p3, which states how the type
name 'T' is looked up in the expression

  t.~T()

Previously, we weren't looking into the type of "t", and therefore
would fail when T actually referred to an injected-class-name. Fixes
PR5530.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@89493 91177308-0d34-0410-b5e6-96231b3b80d8