swift234

Consider default argument patterns, as they relate to actual arguments, when deciding on a specific overload to favor for a function application. Doing so addresses another class of exponential behavior bugs in the type checker (rdar://problem/19779591 and rdar://problem/20772053). There's still some work left to do, though - hence the change to Concatenate.swift, to work around rdar://problem/20789500.

Swift SVN r28221