swift234

Turn on the constraint-based type checker by default <rdar://problem/13324871>.

Lots of tests (46 of them) fail with the constraint-based type
checker, either due to changes in diagnostics or due to outright
bugs in the constraint-based type checker. Use -no-constraint-checker
for these tests.

Note that the hack to parse imported swift.swift with
-no-constraint-checker remains in place, for build-performance
reasons.



Swift SVN r4300