vchoi_fork

[svn-r2348] The way the pthread_t object was being initialized wasn't correct for all
platforms. Also, it's not entirely certain that a value of 0 isn't a
valid thread ID. So, I changed the pthread_t object to be a pointer to
pthread_t with the appropriate memory management this entails. Part of
the validity of this approach rests on the fact that one can assign a
variable which is a structure to another variable of the same type and
all fields within will be copied appropriately...See! C *does* do some
things correctly :-).