Updated proposal for lines (underlining, crossing-out, overline)

[David Faure <faure@kde.org>]

As discussed, here's an updated proposal for the underlining/crossing-out-overline
specification, more based on CSS3.

text-underline-type: none | single | double
text-underline-style: none | solid | dotted | dashed | long-dash | dot-dash | dot-dot-dash | wave
text-underline-width: auto | thick
   or the full CSS3 spec: auto | <normal> | <number> | <length> | <percentage> | thin | medium | thick
   (does any office suite need so much precision on the line widths?)
text-underline-color already defined (3.10.23)
text-underline-mode: continuous | skip-white-space

Notes:
* text-underline-type isn't in CSS3, I have kept it separated so that
  "double dotted" is a possible combination, I feel this is more flexible than
  the CSS3 mechanism of having "double" in text-underline-style
* the "auto" value for text-underline-width allows "double" underline to take
  more space than "single" underline, says the CSS3 specification. I might be
  a better naming for the default width. Thick would be what we call bold.
* text-underline-mode would replace fo:score-spaces (3.10.25).
The reason is that it's IMHO easier to have all settings relating to underline
as text-underline-*, and it separates "should I underline spaces" from
"should I cross out spaces". We have this distinction in KWord already,
and at the moment we have to bundle the two into fo:score-spaces. It's a
small difference, but I figure we should go for the most flexible approach.
* You can add small-wave to text-underline-style if you see the need for it.
* I have added long-dash, it's not in CSS3 (but it's in OO).
* Given that this comes from CSS (and not from XSLFO), I assume the proper
namespace for those attributes is "style:", right? I haven't seen any "css:"
namespace, and the possible values for text-underline-style are a little bit
different from CSS anyway.

The same can be used with overline instead of underline, for the lines over
the text (IIRC this is possible in OO?).

For crossing out, CSS3 uses the same as above, named text-line-through-*, 
but this is only a starting point for us, we need to add the possibility to 
cross out with characters, which I'll let Michael look into.
Tab stop leaders will need something very similar to the crossing out spec.

-- 
David FAURE, faure@kde.org, sponsored by Trolltech to work on KDE,
Konqueror (http://www.konqueror.org), and KOffice (http://www.koffice.org).