Unicode sequences, @typeface, and the font/typeface distinction

A run of Unicode code points now needs one pair of carets, not one pair
each: ^9053 53EF 9053^ renders the characters adjacently, and a single
character inside such a run stands for itself.  An invalid code point is
an error naming the position that wrote it, rather than an apology
rendered into the finished document; noncharacters are refused alongside
surrogates; and a code point that lands on a Klammertext special is safe
through the re-reads that assemble a document.  The character tables now
produce the precomposed form, so a diacritic written as ^a" and one typed
directly are the same text to a search or a copy-paste.

"kdesc -u" describes how to write a Unicode character, with tables of
glyphs beside the codes that produce them.  It is new and not yet
complete: it predates the sequence form and the typeface klammer below.

A typeface and a style are no longer both called "font".  A typeface is a
family resolved by name; a style code is the one letter naming a type
style.  So @document takes :serif_typeface and its siblings, a table takes
:style, captions take :caption_style and :caption_size, the uniform scale
is :text_scale, and the command is "kdesc --typeface".  This renames
arguments a document may already use; an old name is a located error
rather than a silent omission.

@typeface sets a passage in another typeface for the length of that
passage:

    @typeface Noto Sans Egyptian Hieroglyphs | ^132AA 133CF^ :scale 1.5 @

Writing the klammer is the whole declaration -- the document resolves the
typeface, embeds it in what it produces, and carries its license along.
Two typefaces for scripts no text font covers now ship with Klammertext:
Noto Sans Egyptian Hieroglyphs and Noto Sans Cuneiform.  Every typeface in
the distribution now carries its license file.

(from dev 61e598698891)

mac/argv.h

@@ -63,11 +63,11 @@ public:
     // next -/-- token (zero or more).  get(name) returns the words
     // space-joined; given(name) distinguishes "--name with no words"
     // from an absent --name.  Used for subcommand-style interfaces
-    // (kdesc --font install <dir>).
+    // (kdesc --typeface install <dir>).
     // A variadic option: the words after the flag, up to the next one.
     // `parameter` is shown in the usage line as "[<parameter>]" -- an option
     // whose words are a free argument (a search phrase) should name it, so
-    // the usage says what may follow; a subcommand-style option (--font,
+    // the usage says what may follow; a subcommand-style option (--typeface,
     // --coverage) leaves it empty and documents its words in its own help.
     void var(const std::string& name, const std::string& desc,
              const std::string& parameter = "");