Reduce delta with trunk

Remove unnecessary changes to keep cilkplus closer to master.  Also
remove some dead code.
Fix minor typos and AST dump for CapturedStmt

- Treat the body as one of CapturedStmt's children. Otherwise, this
  statement cannot be visited and will not be dumped.
Remove constructor conv warning, and improve user-defined conv warning

Remove the warning that occurred for a < b, where a or be was converted
before calling operator<().

Improve the warning that occurs when a < b
returns a type that is then converted to bool using a user-defined
conversion. Also added a note that points at the conversion operator's
declaration.
Remove code duplicated during CapturedStmt merge