Rand cleanup
- Kill thread_safe_random (all rands are thread safe).
- get_thread_safe_random() -> get_random().
- Add "uint32 plat_rand()" to get single random uint32.
- Narrow vogl_rand down to random and fast_random.
- Trim vogl_uuid down to just use plat_rand_s().
- Kill get_random().
- Add plat_gettmpdir().
- Add plat_gettmpfname().
- Fix generate_temp_filename() to use new plat_ functions and not hardcode "/tmp/".