Expression evaluation for overloaded C functions (redux)

This is a redux of [Ewan's patch](https://reviews.llvm.org/D17957) , refactored
to properly substitute primitive  types using a hook in the itanium demangler,
and updated after the previous patch went stale

The new `SubsPrimitiveParmItanium` function takes a symbol name and replacement
primitive type parameter as before but parses it using the FastDemangler, which
has been modified to be able to notify clients of parse events (primitive types
at this point).

Additionally, we now use a `set` of `ConstStrings` instead of a `vector` so
that we don't try and resolve the same invalid candidate multiple times.

Differential Revision: https://reviews.llvm.org/D27223
Subscribers: lldb-commits

llvm-svn: 290117