swift234

Actual use location information when looking for local variables.

This addresses the bulk of <rdar://problem/15344950>, which involes us
not being able to find local variable declarations in expressions when
the parser didn't pre-bind them for us.

The fix to name lookup itself insures that a case such as 
  case (var a, a)

doesn't allow the second 'a' to find the first.


Swift SVN r9858