doc: Remove in source documentation and the asciidoc package

The RSB documentation is now in ReST format and part of the RTEMS
Documentation project. See https://docs.rtems.org/.

Remove support for the GPL based asciidoc tool and remove the
asciidoc package from the RSB.

Add the Python Markdown package and update the reporter to use
Markdown for HTML generation. The resuling HTML report is a single
self contained file.

Closes #3047.

source-builder/sb/markdown/extensions/nl2br.py

@@ -0,0 +1,35 @@
+"""
+NL2BR Extension
+===============
+
+A Python-Markdown extension to treat newlines as hard breaks; like
+GitHub-flavored Markdown does.
+
+See <https://pythonhosted.org/Markdown/extensions/nl2br.html>
+for documentation.
+
+Oringinal code Copyright 2011 [Brian Neal](http://deathofagremmie.com/)
+
+All changes Copyright 2011-2014 The Python Markdown Project
+
+License: [BSD](http://www.opensource.org/licenses/bsd-license.php)
+
+"""
+
+from __future__ import absolute_import
+from __future__ import unicode_literals
+from . import Extension
+from ..inlinepatterns import SubstituteTagPattern
+
+BR_RE = r'\n'
+
+
+class Nl2BrExtension(Extension):
+
+    def extendMarkdown(self, md, md_globals):
+        br_tag = SubstituteTagPattern(BR_RE, 'br')
+        md.inlinePatterns.add('nl', br_tag, '_end')
+
+
+def makeExtension(*args, **kwargs):
+    return Nl2BrExtension(*args, **kwargs)