Option sets: a .o target for shared parameters

A named group of optional parameters, declared once and used by several
klammers, so a writer learns one vocabulary instead of a spelling per
klammer.  The "o" target is a pseudo-target beside "k": "k" declares a
klammer's interface and documents it, "o" declares an option interface and
documents it, and neither produces output for any target.

    @@caption_args.o :caption :number.bool true :caption_side.side
    : Arguments that define a caption for a block element @@

    @@code.k :filename @hpos_args :hpos left @ @caption_args :caption_side top @
    | text.literal : A source file displayed verbatim @@

A set is used only in the parameter list of a ".k" declaration -- the one
place a klammer's interface is declared once for all of its targets -- and
is resolved as that list is read.  Names and types come from the set; a
default may be overridden where it is used.  A klammer application in a
parameter list is now a definition-time error.

The SKS gains the sets caption_args and hpos_args (:hpos and :offset), and
@table, @image, @image_grid, @reference and @show gain .k declarations.  A
distance is no longer written as a position: :hpos 4em is rejected, and the
same layout is :hpos left :offset 4em.  Code listings are numbered by
default, like tables and figures.

New engine sources mac/option_set{,_registry}.{h,cpp}; tst/ ships two more
suites, option_set_test.sh and signature_test.sh (twelve in all).

 (from dev 34e536cb0329)

sks/code/code.k

@@ -1,128 +1,20 @@
 
-@@code.k :filename :pattern :caption :number.bool | text.literal :
+@@code.k :filename :pattern
+  @hpos_args :hpos left @
+  @caption_args :caption_side top @
+  | text.literal :
 A source file displayed verbatim
 @@
 
-@@code :: @eval code_format.Code(K) @ @@
+@@code :: @eval code_block.Code(K) @ @@
 
 @@c.k code_text :
 A word or phrase displayed verbatim in a line
 @@
 
-@@c :: @eval code_format.Code_fragment(K) eval@
+@@c :: @eval code_block.Code_fragment(K) eval@
 @@
 
 # :cwd makes the filename resolve against the DOCUMENT's directory, not
 # the directory ktext happens to run in.
-@@source_file filename : @eval :cwd *K_input_dir* code_format.Source(K) @ @@
-
-
-#[
-@@code.k text :file :number.bool true :caption : Code listing with formatted comments @@
-
-@@code :
-@eval code_format.Code(K) eval@
-@@
-
-
-@@lst spec.figure_id :
- @reference *spec* | Listing @
-@@
-
-
-
-c <text>
-code <text> :caption :filename :pattern
-
-
-# --------------------------------------------------------------------------------
-@@codebox.k s :color 1,1,1 :size normalsize :escapechar ^^
-              :space_break_only.bool false :linenumber.bool false :scale 1.0
-              :indent :standalone :vcenter :
-Verbatim text for source code preserving whitepace, surrounded by a box
-that extends to the margins @@
-
-@@codebox.html ::
-  @code :text *s* @
-@@
-
-@@codebox.tex ::
-\definecolor{codeboxbgcolor}{rgb}{*color*}
-\setlength{\codeboxlinelength}{\linewidth - 6pt}
-\vspace*{4pt}
-\begin{lstlisting}%
-[frame=single,
-framerule=1pt,
-basicstyle=\*size*\ttfamily,
-lineskip=0pt,
-linewidth=*scale*\codeboxlinelength,
-columns=fullflexible,
-keepspaces=true,
-framesep=6pt,
-xleftmargin=6pt,
-escapechar=*escapechar*,
-breaklines=true,
-prebreak=\hbox{\large$\mapsto$},
-%postbreak={\textbf{\hbox{$\rightarrow$}}},
-rulecolor=\color{codeboxcolor},
-backgroundcolor=\color{codeboxbgcolor},
-breakatwhitespace=*space_break_only*,
-numbers=none, # #- @if *linenumber* | left | none @ #- ,
-numbersep=12pt,
-numberstyle=\small\color{Darkred}]
-*s*
-\end{lstlisting}
-@@
-
-@@codebox.txt ::
-  @code :text *s* @
-@@
-
-@@pathname.k s :small.bool false : Pathname @@
-@@pathname :: @eval code_format.Pathname(K) eval@ @@
-
-@@annotate.k text :caption :
-Comments put in boxes to the right of the code
-@@
-
-# @@annotate : @eval code_format.Annotate(K) eval@ @@
-# @@annotate : @codebox *text* @ @@
-@@annotate :: @code :text *text @ @@
-
-@@listing s : @code :text *s* @ @@
-
-# --------------------------------------------------------------------------------
-@@sv.k s : Italic font for variable in @t syntax @ argument @@
-@@sv.tex  :: ^^textrm"^^textit"*s*$$ @@
-@@sv.html :: @ri *s* @ @@
-
-@@svs.k s : Sans-serif font for variable in @t syntax @ argument @@
-@@svs.tex  :: "^^small^^textsf"^^textit"*s*$$$ @@
-@@svs.html :: @s @i *s* @ @ @@
-
-@@svsub.k base | sub : Italic font for subscripted variable in @t syntax @ argument @@
-@@svsub.tex  :: ^^textrm"^^textit"*base*$$^^textsubscript"*sub*$ @@
-@@svsub.html :: <span class="ritalic">*base*</span><sub>*sub*</sub> @@
-
-@@syntax.k s :fontsize normalsize :indent.bool true :
-Verbatim text that includes italic font for syntax descriptions @@
-
-@@syntax.html ::
-@code :text *s* @ # :indent *indent* @
-@@
-
-@@syntax.tex ::
-\vspace*{8pt}\begin{LVerbatim}[xleftmargin=0pt, # @if true | 0pt | -24pt @ , 
-baselinestretch=1.05, fontsize=\*fontsize*, frame=single, framesep=8pt,
-commandchars=\\̈\$, fontfamily = @verbatimfont@, framesep=12pt]
-*s*
-\end{LVerbatim}
-@@
-
-@@svspace.tex length :
-  ^^vspace*"*length*$
-@@
-
-@@svspace.html length :
-@@
-]#
+@@source_file filename : @eval :cwd *K_input_dir* code_block.Source(K) @ @@