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.cpp

@@ -114,7 +114,7 @@ void check_cpp_arguments(katom_list args, Locator loc)
 }
 
 
-katom_list Eval::eval(katom_iter begin, katom_iter end)
+std::string Eval::eval_command(katom_iter begin, katom_iter end)
 {
     (void)K::log(3, *begin, *(end - 1));
     //msg() << "in Eval::eval:\n" << ktype << kall << kindex << std::pair(begin, end) << "\n";
@@ -150,6 +150,12 @@ katom_list Eval::eval(katom_iter begin, katom_iter end)
         Eval_cpp E_cpp(m_machine, begin->m_loc);
         eval_result = E_cpp.eval(libpath, funcname);
     }
+    return eval_result;
+}
+
+katom_list Eval::eval(katom_iter begin, katom_iter end)
+{
+    std::string eval_result = eval_command(begin, end);
     katom_list result {};
     Machine M = m_machine;
     size_t before = M.m_katoms.size();