[slime-devel] created function echo-area-width

I’ve been playing around with having the minibuffer in its own frame that spans the width of my display, but I noticed the slime one-liners were still being truncated to the width of a normal frame. This change uses the width of the minibuffer window that's associated with the current frame (since it is not necessarily the same width as the current frame).

Also, I noticed this was a little weird, but haven't looked into it yet. This is what's offered as the arglist for with-open-file on a relatively-recent CCL:

(with-open-file (var &key direction element-type if-exists if-does- not-exist external-format class sharing basic) &body body)

It seems to be missing the all-important filespec parameter.