Add tdemarkdown part - embeddable lightweight markdown viewing component.

TDEMarkdown is based on the md4c library and using TDEHTML for rendering
its output. For enhanced safety, on HTML widget is turned off everything
we don't need for viewing. It integrates nicely into Konqueror and
supports both Commonmark and GitHub markdown syntaxes.

Signed-off-by: Mavridis Philippe <mavridisf@gmail.com>

Prepare to merge tdemarkdown into tdelibs.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

1 files changed, 107 insertions, 0 deletions

diff --git a/tdemarkdown/md4c/test/permissive-www-autolinks.txt b/tdemarkdown/md4c/test/permissive-www-autolinks.txt
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+
+# Permissive WWW Autolinks
+
+With the flag `MD_FLAG_PERMISSIVEWWWAUTOLINKS`, MD4C enables recognition of
+autolinks starting with `www.`, even if they do not exactly follow the syntax
+of autolink as specified in CommonMark specification.
+
+These do not have to be enclosed in `<` and `>`, and they even do not need
+any preceding scheme specification.
+
+The WWW autolink will be recognized when the text `www.` is found followed by a
+valid domain. A valid domain consists of segments of alphanumeric characters,
+underscores (`_`) and hyphens (`-`) separated by periods (`.`). There must be
+at least one period, and no underscores may be present in the last two segments
+of the domain.
+
+The scheme `http` will be inserted automatically:
+
+```````````````````````````````` example
+www.commonmark.org
+.
+<p><a href="http://www.commonmark.org">www.commonmark.org</a></p>
+````````````````````````````````
+
+After a valid domain, zero or more non-space non-`<` characters may follow:
+
+```````````````````````````````` example
+Visit www.commonmark.org/help for more information.
+.
+<p>Visit <a href="http://www.commonmark.org/help">www.commonmark.org/help</a> for more information.</p>
+````````````````````````````````
+
+We then apply extended autolink path validation as follows:
+
+Trailing punctuation (specifically, `?`, `!`, `.`, `,`, `:`, `*`, `_`, and `~`)
+will not be considered part of the autolink, though they may be included in the
+interior of the link:
+
+```````````````````````````````` example
+Visit www.commonmark.org.
+
+Visit www.commonmark.org/a.b.
+.
+<p>Visit <a href="http://www.commonmark.org">www.commonmark.org</a>.</p>
+<p>Visit <a href="http://www.commonmark.org/a.b">www.commonmark.org/a.b</a>.</p>
+````````````````````````````````
+
+When an autolink ends in `)`, we scan the entire autolink for the total number
+of parentheses.  If there is a greater number of closing parentheses than
+opening ones, we don't consider the last character part of the autolink, in
+order to facilitate including an autolink inside a parenthesis:
+
+```````````````````````````````` example
+www.google.com/search?q=Markup+(business)
+
+(www.google.com/search?q=Markup+(business))
+.
+<p><a href="http://www.google.com/search?q=Markup+(business)">www.google.com/search?q=Markup+(business)</a></p>
+<p>(<a href="http://www.google.com/search?q=Markup+(business)">www.google.com/search?q=Markup+(business)</a>)</p>
+````````````````````````````````
+
+This check is only done when the link ends in a closing parentheses `)`, so if
+the only parentheses are in the interior of the autolink, no special rules are
+applied:
+
+```````````````````````````````` example
+www.google.com/search?q=(business))+ok
+.
+<p><a href="http://www.google.com/search?q=(business))+ok">www.google.com/search?q=(business))+ok</a></p>
+````````````````````````````````
+
+If an autolink ends in a semicolon (`;`), we check to see if it appears to
+resemble an [entity reference][entity references]; if the preceding text is `&`
+followed by one or more alphanumeric characters.  If so, it is excluded from
+the autolink:
+
+```````````````````````````````` example
+www.google.com/search?q=commonmark&hl=en
+
+www.google.com/search?q=commonmark&hl;
+.
+<p><a href="http://www.google.com/search?q=commonmark&amp;hl=en">www.google.com/search?q=commonmark&amp;hl=en</a></p>
+<p><a href="http://www.google.com/search?q=commonmark">www.google.com/search?q=commonmark</a>&amp;hl;</p>
+````````````````````````````````
+
+`<` immediately ends an autolink.
+
+```````````````````````````````` example
+www.commonmark.org/he<lp
+.
+<p><a href="http://www.commonmark.org/he">www.commonmark.org/he</a>&lt;lp</p>
+````````````````````````````````
+
+
+## GitHub Issues
+
+### [Issue 53](https://github.com/mity/md4c/issues/53)
+```````````````````````````````` example
+This is [link](www.github.com/).
+.
+<p>This is <a href="www.github.com/">link</a>.</p>
+````````````````````````````````
+```````````````````````````````` example
+This is [link](www.github.com/)X
+.
+<p>This is <a href="www.github.com/">link</a>X</p>
+````````````````````````````````