Escaping, table layout, and document fixes

Quoted Klammertext specials (^@ ^| ^# ^^ ^: ^*) and ^'...'^ regions now
survive re-processing (held as escape markers until final output);
:after_apply phase functions receive and return raw target text.

Tables: :hpos element position (center|left|right|<length>) replaces the
unimplemented :center/:indent; the ranged cell override is renamed
:justify; :column_width works in html (colgroup widths) and gains
'fill' -- the remaining width, capped at the column's widest entry, in
both targets; a table wider than the text column warns on the console;
table edges without an outer line set their text flush on the margins.

@document: no empty title bar for untitled documents; @vfill fills to
the bottom of the window in html (pure CSS); @vspace in plain text;
new @dot klammer; monospace email links.

mac/eval.h

@@ -25,6 +25,14 @@ public:
     std::vector<Katom> eval(
         std::vector<Katom>::iterator begin, std::vector<Katom>::iterator end);
 
+    // Dispatch the @eval command (python/shell/haskell/cpp) and return its
+    // raw string result, without re-reading it as Klammertext.  Used by
+    // :after_apply phase functions, whose input and output are final target
+    // text -- re-katomizing it would misparse target characters (a "@" in
+    // justified txt output) as Klammertext syntax.
+    std::string eval_command(
+        std::vector<Katom>::iterator begin, std::vector<Katom>::iterator end);
+
     Machine m_machine;
     Locator m_loc;
 };