[Groff] -Txhtml

[Gaius Mulley]

Hi,

here are some proposed patches which introduce the xhtml device.
The features of -Txhtml are as follows:

    *  -Txhtml is honoured in groff, which passes the appropriate
       dialect options '-x x' to pre-grohtml and post-grohtml.

    *  the device register is set to `html' but the number register
       xhtml is also defined to 1, so the default html support macros
       can all be reused.

    *  it utilises esr's mathml switch to eqn providing that the equation
       is not in a picture or any other image (otherwise the image
       contains the image of the equation as per -Thtml).  MathML is
       now emitted!  I've had to modify eqn in a very small way to
       make it emit the mathml as a parameter to a xhtml support
       macro.  These modifications are enabled by the eqn option
       -Tmathml:xhtml (this is automatically done by the front end
       groff).

    *  introduced the -V option to post-grohtml which issues a xhtml
       1.1 validate button at the bottom of the document.  Tested
       against large documents such as pic.ms, but it currently
       produces illegal xhtml when the document is split into
       sections.  I'll look into this and hopefully fix the huge files
       issue at the same time as the xhtml split up - this area
       looks like a good candidate for a rewrite.
       Nevertheless, ignoring the section split, I think it should
       produce valid xhtml 1.1.  Certainly it should be seen as a
       statement of intent :-)

    *  cleaned up a number of tags in post-grohtml for both -Txhtml
       and -Thtml.

    *  added internal support macros to www.tmac

    *  added new number register \n[.O] which retrieves the image
       nesting level (used with escapes \O etc).

    *  updated the grohtml manual page to reflect dialect option and
       validate option.

I'd value any feedback,

enjoy,
Gaius

latest_patch_6
Description: patch for xhtml