Introduce a new kind of cursor into libclang, which covers a reference

to an "overloaded" set of declarations. This cursor kind works for
unresolved references to functions/templates (e.g., a call within a
template), using declarations, and Objective-C class and protocol
forward declarations.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@113805 91177308-0d34-0410-b5e6-96231b3b80d8