swift234

Two changes that got mixed up:
#1: Change type conversion errors to print the types involved, making the diagnostic better.  We still don't have ranges, but it is progress.

#2: Reimplement support for anonymous closure arguments (e.g. func($0+$1)) where func takes a closure, step #1.
 - This removes AnonDecl, replacing it with AnonClosureArgExpr.  $0 and friends have to be expressions since they don't get a type and don't get resolved until TypeChecking.
 - For now we just replace the existing broken support, a future step is to implement type checking support for them.


Swift SVN r278