swift234

Generalize constraint application under -strict-keyword-arguments.

Introduce a new locator kind for argument/parameter comparisons that
tracks both the argument and the parameter, which we will eventually
use in diagnostics more regularly. For now, this helps us smooth over
scalar-to-tuple/tuple-to-tuple/tuple-to-scalar nonsense when dealing
with calls.

Fix a pile of fallout from this change.

Swift SVN r17648