Use server core dumping instead of process freeze in gdb

[QuakeIV]

There is a certain philosophy that auto-restarting a server due to a fault is a bad idea, due to probability that the fault will immediately re-arise and crash it again.

I personally think its a relatively reasonable one, many faults are repeatable so trying to reboot wont do much good, and it will do some small degree of harm to the servers to reboot them repeatedly for hours.