RFA: infrun.c: mourn instead of kill after TARGET_WAITKIND_SIGNALLED

[Eli Zaretskii]

> According to target.h, TARGET_WAITKIND_SIGNALLED does indeed mean that the
> program has terminated, and all current uses of TARGET_WAITKIND_SIGNALLED
> seem to honor that meaning.  Here's where it gets used:
> 
>   in target.c:store_waitstatus() when inferior status is !WIFEXITED() &&
>     !WIFSTOPPED()
>   in gnu-nat.c:inf_task_died_status() when a task has died
>   in go32_wait() #if __DJGPP_MINOR__ < 3; I assume this works around
>     a lack in older djgpp implementations

The debug support routines in DJGPP versions before 2.03 had a grave
limitation: whenever the debuggee got any signal, it would die on the
spot, even if it had installed a handler for that signal.  DJGPP v2.03
and later don't have this problem, so TARGET_WAITKIND_SIGNALLED is not
used anymore in the DJGPP version of GDB.

In other words, I have no problems whatsoever with this change ;-).