bug#25481: `guile --listen' broken on guile master

[Christopher Allan Webber]

(originally accidentally sent to guile-devel instead of here, sorry for
xpost!)

If you use the latest Guile, you'll find that "guile --listen" has
broken.  If you try:
  ./meta/guile --listen=/tmp/guile-socket

then you'll find that you have a very short window in which you can do:
  M-x geiser-connect-local <RET> guile <RET> /tmp/guile-socket <RET>

but then the main repl, the one you launched in the shell, hangs.
And if you wait too long or disconnect then reconnect, you won't be
able to connect again.

What you'll see in the guile process is this:

  scheme@(guile-user)> In thread:
  ERROR: In procedure select: Interrupted system call

Here's the commit that introduces the bug:
206dced87f425af7eed628530313067a45bee2c2

I've verified that it works right before that commit.

The commit does some things involving changing the code involving the
"select" and etc in the repl code, so maybe that's related.