Fix stack overrun bug in while parsing multiple groups
Fix stack overrun bug in while parsing multiple groups

mcjoin can act on multiple groups, these groups are input as command
line arguments.  The mechanism for G+N is always executed, but when
there is no +N and the next group is longer than the previous one
the stack is overrun in inet_ntop().

This patch lets mcjoin operate on a copy of the group from the command
line and inet_ntop() operate on a big enough buffer at the end.

Signed-off-by: Joachim Wiberg <583c295fd7602c168ad814279bbc3894ba65f5d6@gmail.com>

troglobit/mcjoin,troglobit/mcjoin