swift234

- Add integer <-> integer conversion functions for Int32 and Int64.
- add a top level abort() method.
- add an assert() implementation
- Add a "Char" typedef for Int32, switch printChar to use it.
- Add a method to String to extract an element out of it (currently named
  getElement, to be named [] eventually)
- Implement String.replPrint in terms of string operations.


Swift SVN r1545