Bundle Latest REXML

Sam Ruby has been doing a bang-up job fixing the bugs in REXML.
Who knows when these improvements will trickle down to vendor distributions of Ruby.
In the meantime, let's bundle the latest version of REXML with Instiki.
We check the version number of the bundled REXML against that of the System REXML, and use whichever is later.

vendor/plugins/maruku/tests/unittest/references/long_example.md

@@ -85,4 +85,36 @@ inspiration for Markdown's syntax is the format of plain text email.</p>
 <p>To this end, Markdown's syntax is comprised entirely of punctuation</p>
 
 *** Output of Markdown.pl (parsed) ***
-Error: #<NoMethodError: private method `write_children' called for <div> ... </>:REXML::Element>
+<div>
+ <p>
+  filters -- including 
+  <a href='http://docutils.sourceforge.net/mirror/setext.html'>
+   Setext
+  </a>
+  , 
+  <a href='http://www.aaronsw.com/2002/atx/'>
+   atx
+  </a>
+  , 
+  <a href='http://textism.com/tools/textile/'>
+   Textile
+  </a>
+  , 
+  <a href='http://docutils.sourceforge.net/rst.html'>
+   reStructuredText
+  </a>
+  , 
+  <a href='http://www.triptico.com/software/grutatxt.html'>
+   Grutatext
+  </a>
+  , and 
+  <a href='http://ettext.taint.org/doc/'>
+   EtText
+  </a>
+   -- the single biggest source of inspiration for Markdown's syntax is the
+  format of plain text email.
+ </p>
+ <p>
+  To this end, Markdown's syntax is comprised entirely of punctuation
+ </p>
+</div>

vendor/plugins/maruku/tests/unittest/references/spaces_and_numbers.md

@@ -25,4 +25,4 @@ md_el(:document,[md_ref_def("6", "http://ettext.taint.org/doc/", {:title=>nil})]
 
 
 *** Output of Markdown.pl (parsed) ***
-Error: #<NoMethodError: private method `write_children' called for <div/>:REXML::Element>
+<div/>