* inf-ptrace.c [PT_GET_PROCESS_STATE] (inf_ptrace_follow_fork):

New function.
(inf_ptrace_him, inf_ptrace_attach) [PT_GET_PROCESS_STATE]: Set
PTRACE_FORK event flag.
(inf_ptrace_wait) [PT_GET_PROCESS_STATE]: Handle PTRACE_FORK
event.
(inf_ptrace_target) [PT_GET_PROCESS_STATE]: Set to_follow_fork.