[slachiewicz]

Three cases where the sink escaped characters that are not special in
Markdown, making generated documents noisy and hard to hand-edit:

• " and ' were turned into " and '. Markdown is not XML; both
  are ordinary characters there. Only <, > and & still get escaped, so
  text is never mistaken for raw HTML.
• ( and ) were escaped everywhere. They are only special inside a link
  destination, and destinations are written without going through the
  text escaping, so 'JDK (i.e. Java 6)' no longer becomes 'JDK (i.e.
  Java 6)'.
• . was escaped after any digit, so a version such as 1.6 came out as
  1.6. It only needs escaping when it would turn leading digits into an
  ordered list marker, i.e. when only whitespace and digits precede it.

Adjusted the one affected expectation in MarkdownSinkTest.

A second change in the same area: a space ends the destination of a Markdown
inline link and starts the optional title, so a destination carrying one does
not resolve. APT allows spaces in both anchors and URLs, so converting a
document like

The {{{#Identity Mapper}Identity Mapper}}

produced [Identity Mapper](#Identity Mapper), which links nowhere. An in-page
anchor now gets the same encoding an anchor definition receives, which is also
what the HTML renderer applies to the anchor it points at, and any other
destination has its spaces percent-encoded.

Part of the wider migration tracked in
apache/maven-doxia-converter#139