[PATCH] ash: add process substitution in bash-compatibility mode

[Ron Yorston]

Denys wrote:
>Can we use popredir() mechanism instead?

It's possible but it adds more complication to already complex code.
Currently the stack of redir fds is always unwound unconditionally.
The procsub fds are conditionally removed depending on whether or not
we're in a shell function.  This requires popredir() to be capable
of removing some entries from the linked list while leaving others.
Plus there's the additional bookkeeping for the different types of fd.

I think a cleaner approach is to have a separate linked list for the
procsub fds.

Ron