* doc/groff.texinfo: Document new .O register and add cross

* doc/groff.texinfo: Document new .O register and add cross
reference entries.

* NEWS: Updated.

* src/devices/grohtml/grohtml.man: Document new -V and -y options.

* src/devices/grohtml/html-table.cpp: Add support for XHTML 1.1.
(html_table:: emit_colspan, html_table::emit_td): New methods.
(html_table::emit_col):  Use html_table::emit_td.
(html_table::emit_table_header): Use html_table::emit_colspan if
dialect xhtml is specified.
(html_table::finish_row): Updated.

* src/devices/grohtml/html-table.h (html_table): Declare
emit_colspan, emit_td.

* src/devices/grohtml/html-text.cpp: Modified tags to comply with
xhtml if this dialect was requested.

* src/devices/grohtml/html-text.h (html_dialect): New enumeration.
(html_text): Add new variable `dialect'.

* src/devices/grohtml/post-html.cpp: Modify header tags to be XHTML
compliant.
(valid_flag, groff_sig, dialect): New global variables.
(html_printer::handle_valid_flag, html_printer::do_math,
html_printer::write_html_anchor, html_printer::write_xhtml_anchor,
html_printer::do_math, html_printer::handle_valid_flag): New
methods.
(html_printer::emit_line, html_printer::emit_raw,
html_printer::do_check_center, html_printer::write_title,
write_rule, html_printer::writeHeadMetaStyle, generate_img_src,
html_printer::begin_page): Altered to be XHTML compliant.
(html_printer::write_header): Updated.
(html_printer::troff_tag): Call do_math.
(html_printer::insert_split_file, html_printer::do_file_components,
html_printer::write_navigation): Create XHTML file components if
necessary and also produces a groff signature if requested.
(~html_printer): Call writeHeadMetaStyle at appropriate places
depending upon html_dialect.
(html_printer::special): Handle new tags `html<?p>' and `math<?p>'.
(main): Added options -x, -V, and -y.
(usage): Updated.

* src/preproc/eqn/box.cpp: Create a distinction between
the MathML device and the XHTML device.
(do_text): Issue a newline at the end of the equation if XHTML was
specified.
(box::top_level): Prefix the output of an equation by the .MATHML
macro.
(output_string): Suppress \n if XHTML was specified.

* src/preproc/eqn/main.cpp (xhtml): New global flag.
(inline_equation): Skip leading spaces after inline equation for
XHTML device.
(main): Set `xhtml' flag if `-Tmathml:xhtml' is specified.

* src/preproc/eqn/eqn.h (xhtml): New external flag.

* src/preproc/eqn/text.cpp (entity_table): Fix typo.

* src/preproc/html/pre-html.cpp (html_dialect): New enumeration.
(dialect, eqn_flag): New global variables.
(html_system): Improve debugging support.
(alterDeviceTo): Test for -Txhtml when altering device to the image
device and reset to -Txhtml.
(addZ): Renamed to...
(addArg): This.
Introducea a general parameter.
(print_args): New debugging function.
(char_buffer::run_output_filter): Use print_args and addArg rather
than addZ.
(char_buffer::do_html, char_buffer::do_image): Add -rxhtml=1 command
line parameter as an argument to the html generation of text when
xhtml is needed.  Include -e on the command line if mathml is
required.
(scanArguments): Allow -e, -V, -y and -x options.
-V, -y are handled by the back end.  -e sets `eqn_flag'.
-x determines HTML dialect.

* src/roff/groff/groff.cpp (possible_command): New method
`clear_name'.
(main):  Set eflag if -e is present on command line.
Set is_xhtml if -Txhtml is present.
Pass `-x x' to the HTML pre and post processors.
Pass `-e' to the HTML pre processor if required.
Pass `-Tmathml:xhtml' to eqn if XHTML is requested.

* src/roff/troff/input.cpp (init_input_requests): Introduce new
number register `\n[.O]'.

* tmac/s.tmac: (LP): Use .nop for semantic sugar.
(cov*ab-init) reformat.
(@EQ): Use EQN-HTML-IMAGE and friends rather than HTML-IMAGE.
(CHECK-FOOTER-AND-KEEP): Define FS, FE such that they use
<cite></cite> for the html device rather than generate images for
footnotes.

* tmac/troffrc-end: Define EQN-HTML-IMAGE,
EQN-HTML-IMAGE-END, EQN-HTML-IMAGE-RIGHT,
EQN-HTML-IMAGE-LEFT, EQN-HTML-IMAGE-INLINE,
EQN-HTML-DO-IMAGE, EQN-HTML-IMAGE-END as null strings.

* tmac/www.tmac: (HTML<?p>): New macro.
(MATH<?p>): New macro.
(IMG, PIMG, MPIMG, HR): Use XHTML compliant syntax.
(www-emit-ltag): New macro.
(www-push-li): Updated.
(ULS): Ensure that tags are balanced in order by use of
www-emit-ltag.
(ULE): Likewise: Use www-emit-ltag and shut down paragraphs in
order.
(OLS, OLE, DLS, DLE): Ditto.
<global>: Define EQ and EN to EQN-HTML-IMAGE and EQN-HTML-IMAGE-END
respectively.
(www-li-ul, www-li-ol, www-li-dl): Updated.
(EQN-HTML-IMAGE, EQN-HTML-IMAGE-RIGHT, EQN-HTML-IMAGE-LEFT,
EQN-HTML-IMAGE-INLINE, EQN-HTML-DO-IMAGE, EQN-HTML-IMAGE-END,
MATHML): New macros.