Verbatim-safe typography, ^-punctuation quoting, full-range ^UUUU^, polyglot html

Typographic transforms (---, quote pairs, ~) no longer touch verbatim
text: @c/@code/@source_listing content and ^'...'^ spans show exactly the
characters written. "^" before any punctuation character quotes it in
every target (the apostrophe excepted: ^' opens a literal span), with the
new :resolve option on @@@target declaring per-target renderings. The
^UUUU^ code-point form accepts 4-6 hex digits, the full Unicode range.
The html output and transform spellings are polyglot (XML-valid), in
preparation for an EPUB target. New suites: transform_test, character_test
(engine), typography_test (SKS).

(from dev 07ce5ea86a0a)

sks/section/section.k

@@ -12,6 +12,9 @@
 @@s1.k title :id :n : Top level division, numbered  @@
 @@s1.html,tex :: @eval section.Section(K, 1) eval@ @@
 
+# Temporary hack for testing txt target; need to number section headings.
+@@s1.txt :: *title* @@
+
 @@s2.k title :id :n : Second level division, numbered  @@
 @@s2.html,tex :: @eval section.Section(K, 2) eval@ @@