1.0.25.18: it's only SHOW

1.0.25.18: it's only SHOW

- fix compilation with QSHOW

- SHOW prints thread id on threaded builds

- SHOWing os_threads

  - do not print pthread_self() that's the job of SHOW
  - always print thread ids with %lu
  - states with %x

- add more SHOW to ease debugging

- gc_stop_the_world: don't flood with FSHOW_SIGNAL when waiting for
  another thread to change states

- signal safe SHOW

  (if QSHOW_SAFE is defined)