Implement special-case name lookup for inheriting constructors: member
using-declarations with names which look constructor-like are interpreted as
constructor names.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177957 91177308-0d34-0410-b5e6-96231b3b80d8
Remove FIXMEs: these are covered by a core issue which we don't yet implement
(but we happen to get this part right).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177958 91177308-0d34-0410-b5e6-96231b3b80d8