Document {} behaving as literals in some contexts.

Regen docs.

doc/html/boost_regex/syntax/perl_syntax.html

@@ -176,6 +176,13 @@
 <pre class="programlisting"><span class="identifier">a</span>
 <span class="identifier">aaaa</span>
 </pre>
+<p>
+        Note that the "{" and "}" characters will treated as
+        ordinary literals when used in a context that is not a repeat: this matches
+        Perl 5.x behavior. For example in the expressions "ab{1", "ab1}"
+        and "a{b}c" the curly brackets are all treated as literals and
+        <span class="emphasis"><em>no error will be raised</em></span>.
+      </p>
 <p>
         It is an error to use a repeat operator, if the preceding construct can not
         be repeated, for example:

doc/html/index.html

@@ -198,7 +198,7 @@
   </p>
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
-<td align="left"><p><small>Last revised: May 23, 2014 at 12:15:55 GMT</small></p></td>
+<td align="left"><p><small>Last revised: September 25, 2014 at 10:52:51 GMT</small></p></td>
 <td align="right"><div class="copyright-footer"></div></td>
 </tr></table>
 <hr>

doc/syntax_perl.qbk

@@ -115,6 +115,11 @@ But neither of:
    a
    aaaa
 
+Note that the "{" and "}" characters will treated as ordinary literals when used
+in a context that is not a repeat: this matches Perl 5.x behavior.  For example in
+the expressions "ab{1", "ab1}" and "a{b}c" the curly brackets are all treated as
+literals and ['no error will be raised].
+
 It is an error to use a repeat operator, if the preceding construct can not 
 be repeated, for example: