* Type pid_t is not cross-platform. Just use int instead, and convert it
  to respective type on each platform.
* Get rid of several useless include which should have been removed a
  few commits ago, when I reimplemented the backtrace function.
* Better handle the various macros in gimp_eek() (between G_OS_WIN32,
  HAVE_EXCHNDL and GIMP_CONSOLE_COMPILATION, but also no_interface and
  generate_backtrace options, that was a bit messy).
* Make gimpdebug now always built, whatever the platform.