Implement NetBSDHardware subclass into library/system/setup, to provide
Ansible with more NetBSD facts.
The setup module has been updated to provide the following info:
    - memfree_mb
    - memtotal_mb
    - swapfree_mb
    - swaptotal_mb
    - processor (a list)
    - processor_cores
    - processor_count
    - devices

As a matter of fact, mem, swap and processor are available the same as
on Linux. Tested on NetBSD-6.1, 6.0 and 5.0_STABLE (without Linux
emulation).