swift234

This patch fixes the playground transform to support
transforming top-level code.  This involves these
changes:

- The playground transform now looks for functions
  and top level code throughout the source file
  rather than identifying a single function whose
  body needs to be transformed.  

- The playground transform now does not look for
  VarDecls to transform; rather it looks for
  PatternBindingDecls with initializers.  This
  is because the VarDecls are typically at top
  level, where logging code can't be added, but
  the PatternBindingDecls are already in
  TopLevelCodeDecls.

<rdar://problem/16977837>


Swift SVN r18522