Add MAY language for using CLDR symbols and number formats as request…

…ed in #617.

Note that if a CLDR format pattern is used, there is no way to know whether `pattern` is a regular expression or CLDR format. Also, additional symbols are not included in our namespace, and so will be lost through a hypothetical JSON-LD transformation.

syntax/index.html

@@ -775,6 +775,7 @@ <h3>Formats for numeric types</h3>
             <dt><dfn title="datatype format pattern">pattern</dfn></dt>
             <dd>A regular expression string, with syntax and processing defined by [[!ECMASCRIPT]].</dd>
           </dl>
+          <p>In addition, implementations MAY support additional number symbols described by <cite><a href="http://www.unicode.org/reports/tr35/tr35-39/tr35-numbers.html#Number_Symbols">Number Symbols</a></cite> and pattern values described by <cite><a href="http://www.unicode.org/reports/tr35/tr35-39/tr35-numbers.html#Number_Format_Patterns">Number Format Patterns</a></cite> from [[CLDR]]. In this case the <a title="datatype format pattern">pattern</a> property is interpreted accordingly, rather than as a regular expression.</p>
           <p class="note">
             Authors are encouraged to be conservative in the regular expressions that they use, sticking to the basic features of regular expressions that are likely to be supported across implementations.
           </p>
@@ -806,7 +807,7 @@ <h3>Formats for numeric types</h3>
           <ul>
             <li>does not meet the numeric format defined above,</li>
             <li>contains two consecutive <a title="datatype format groupChar">groupChar</a> strings,</li>
-            <li>does not match the regular expression defined in the <a title="datatype format pattern">pattern</a> property, if there is one,</li>
+            <li>does not match the pattern defined in the <a title="datatype format pattern">pattern</a> property, if there is one,</li>
             <li>contains the <a title="datatype format decimalChar">decimalChar</a>, if the <a>datatype base</a> is <code>integer</code> or one of its sub-values,</li>
             <li>contains an exponent, if the <a>datatype base</a> is <code>decimal</code> or one of its sub-values, or</li>
             <li>is one of the special values <code>NaN</code>, <code>INF</code>, or <code>-INF</code>, if the <a>datatype base</a> is <code>decimal</code> or one of its sub-values.</li>