The bro_prng() implementation cannot generate 0 as a result since it
causes every subsequent number from the PRNG to also be 0, so use the
number 1 instead of 0.
The srand()/rand() interface was being intermixed with the
srandom()/random() one. The later is now used throughout.
Changed the srand() and rand() BIFs to work deterministically if Bro
was given a seed file (addresses #825). They also now wrap the
system's srandom() and random() instead of srand() and rand() as per
the above.
