Multio / process substitution bug

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

Given the following which you probably recognize from zsh-users:

alias -g file_err='>(sed s/^/file_err:/)'
alias -g file_out='>(sed s/^/file_out:/)'
alias -g file_mix='>(sed s/^/file_mix:/)'
outanderr() { print STDOUT; print -u2 STDERR }

The following command:

torch% outanderr 1>&1 >file_out 2>&2 2>file_err >& file_mix
STDOUT
file_out:STDOUT
STDERR
file_err:STDERR

is now hung forever waiting in signal_suspend() for the file_mix process
to exit.  Keyboard signals are disabled so the only way to interrupt it
is to kill it from another shell.