I've been doing some work on this new option I'm suggesting.  The
current name I'm leaning towards is PROMPT_SP, so that's what this
patch implements.  Please feel free to comment about this or suggest
a better name.

The patch was also changed to try to output fewer characters, and also
to try to prevent mouse selection from joining a partial line with the
prompt line that follows it (resulting in a lot of spaces being copied
to the clipboard).  So, this patch uses TCMULTRIGHT or TCRIGHT (when
available) to get to (or near) the right margin, outputs 2 spaces (which
might induce a wrap), and then (if save- and restore-cursor are there),
it outputs two backspaces and either tries to clear-to-EOL or to delete
a character before restoring the cursor position.

In my testing, as long as the cursor ends up on the previous line by the
backspaces, both xterm and konsole fix the selection problem using
either clear-to-EOL or delete-char.  However, the only way I currently
know of to enable a wrappable left margin is to run zsh under screen, so
suggestions are welcomed as to how to enable a soft left margin in a
modern day terminal emulator.

One thing I added while I was adding support for looking up the save-
and restore-cursor escapes was a lookup for the backspace character
("bc" is only supposed to be set if the "bs" flag is not set, but I just
made the code always look up "bc" and default the value to "\b" if it
wasn't found).  Since some other parts of zsh use literal \b characters,
this might be overkill and it is debatable if we really need it.

This patch is based on the CVS version, not my prior patch.

..wayne..