docs: add reserved words restrictions for class-alias in PHP 8.5

Update reserved words documentation to include array and callable as reserved
words as of PHP 8.5. Clarify in class_alias() function that aliases cannot
use reserved words, with link to reserved words reference.

Author: jordikroon

appendices/reserved.xml

@@ -567,6 +567,12 @@
         <entry>
          never (as of PHP 8.1)
         </entry>
+        <entry>
+         array (as of PHP 8.5)
+        </entry>
+        <entry>
+         callable (as of PHP 8.5)
+        </entry>
        </row>
       </tbody>
      </tgroup>

reference/classobj/functions/class-alias.xml

@@ -17,6 +17,9 @@
    Creates an alias named <parameter>alias</parameter>
    based on the user defined class <parameter>class</parameter>.
    The aliased class is exactly the same as the original class.
+  </para>
+  <para>
+   The class alias cannot be any of the PHP <link linkend="reserved.other-reserved-words">reserved words</link>.
   </para>
    <note>
    <simpara>