* inf-ttrace.c (inf_ttrace_vfork_ppid): New variable.

(inf_ttrace_follow_fork): New function.
(inf_ttrace_him, inf_ttrace_attach): Ask for TTEVT_FORK and
TTEVT_VFORK events.  Replace TTEO_NOSTRCHLD option with
TTEO_PROC_INHERIT.
(inf_ttrace_create_inferior, inf_ttrace_attach): Add checks for
inf_ttrace_vfork_ppid.
(inf_ttrace_kill_inferior, inf_ttrace_detach): Detach from waiting
parent if appropriate.
(inf_ttrace_wait): Handle TTEVT_FORK and TTEVT_VFORK.
(inf_ttrace_target): Set to_follow_fork.