* Fix GHC trac #2897: Generate a separate "utils" C file containing
  wrappers for functions like printf. This means template-hsc.h
  doesn't need to includes any headers, so we don't pollute the C
  environment.
  (actually, we still need to include stddef.h).

* Use runProcess rather than system. It used to try to conditionally
  use runProcess if it was available, but never actually did. Now it
  uses it unconditionally.

* Some tidying up