bug in aux/listen

bug in aux/listen

[forsyth]

aux/listen does an rfork sharing memory to create the listener for
each service.  that also ensures that
	Subsequent forks by the parent will then
	propagate the shared data and bss between children.
	[rfork(2)]
aux/listen later forks a process to handle each incoming call.
that doesn't specify RFMEM, but is still sharing memory.
perhaps that was expected, but in any case, the later becomenone()
calls newns, which uses bio to read /lib/namespace, and malloc
is called, but the libc.h version doesn't expect to share memory;
mayhem ensues. there are safe versions of malloc (for instance in /sys/src/cmd/ndb), or
one could rewrite listen in Alef, but for now it seems easier just
to be a bit less efficient.  listen doesn't seem to rely on sharing memory.

forse% diff $home/cd/cmd/aux/listen.c /sys/src/cmd/aux/listen.c
100c100
< 		switch(rfork(RFFDG|RFPROC|RFMEM)){
---
> 		switch(rfork(RFFDG|RFPROC)){ /* had RFMEM */