swift234

As soon as we generate a constraint, attempt to simplify that
constraint. This eliminates a lot of redundant looping over
constraints, which can have a non-trivial performance impact: in an
utterly unscientific test of a Debug build type-checking swift.swift,
this minor tweak improves performance by 3x. It doesn't help with the
ridiculously exponential issues, however.


Swift SVN r2923