exportfs used pid of slave proc as rendezvous tag. when we
changed it to use Proc* memory address, there where tag
collisions because listen didnt fork the rendezvous group (bug!).
for now, just do rfork(RFREND) in main just in case.
will fix aux/listen in a follow up changeset.
--
cinap
get rid of the service buffer limit. keep service buffers
on a global freelist protected by lock.
dont fatal when we hit the process limit. instead, just
abort the rpc with an error.
handle rendezvous() interrupts.
fork child exportfs with new rendezvous group.
fix missing close of pipe filedescriptors on error.
fix missing close of other end of pipe in child.
dont bark when we get eof on the first init string read.
this condition can happen when unmount opens and
immidiately closes a exported srv file.
Fix the behavior of exportfs -r.
Check the return of chdir(srv) to prevent exporting accidentally
the current working directory when the directory specified
with option -r doesn't exist.
Also fix at the same time the missing trailing \n in error
messages printed just before exits().
