* lin-lwp.c (count_events_callback): Fix formatting. Turn check

* lin-lwp.c (count_events_callback): Fix formatting.  Turn check
commented with "paranoia" into gdb_assert.
(select_event_lwp_callback): Likewise.
(cancel_breakpoints_callback): Bail out early if LP is the event
LWP.  Add comment about backup up breakpoints.  Fix formatting and
debug message.
(select_event_lwp): Make solely repsonsible for switching event
LWP.  Fix formatting and remove bogus "ERROR" debug message.
Don't backup breakpoints from here.
(lin_lwp_wait): Don't touch LP->status, let select_event_lwp
handle that.  Only call select_event_lwp if we're not waiting for
a specific LWP, i.e. when PID == -1.  Backup breakpoints from here.