swift234

Minor improvements:
 - Remove a weird special case for literals from TypeChecker::typeCheckCondition.
 - Enhance FailureDiagnosis::getTypeOfIndependentSubExpression to know about situations
   where recursive type checks fail (in some nested situation) but still produce a type
   for the top level of the expr tree.
 - Remove dead code from CSApply now that you can't branch on Builtin.Int1.

The first & second combine to slightly improve one case I've been looking at in 
test/expr/expressions.swift.




Swift SVN r29860