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/link/link.py

@@ -13,8 +13,8 @@ def html_link(target, link_text, is_section, no_quotation_marks):
             link_text = target if no_quotation_marks else f"“{target}”"
         else:
             # Allow long URLs to break at a slash:
-            link_text = re.sub('/', '/<wbr>', target)
-            link_text = re.sub('/<wbr>/<wbr>', '//', link_text)
+            link_text = re.sub('/', '/<wbr/>', target)
+            link_text = re.sub('/<wbr/>/<wbr/>', '//', link_text)
             link_text = f'<tt>{link_text}</tt>'
     target = f"[{target}]" if is_section else target
     #result = f"[__link__{target}__{link_text}__]"