Update XML class reference and improve type hinting in function signatures (#252)

Author: sy-records

scripts/docgen/class.tpl

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<phpdoc:classref xml:id="class.{CLASS_NAME_ID}" xmlns:phpdoc="http://php.net/ns/phpdoc" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude">
+<reference role="{CLASS_TYPE}" xml:id="class.{CLASS_NAME_ID}" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude">
  <title>The {CLASS_NAME} {CLASS_TYPE}</title>
  <titleabbrev>{CLASS_NAME}</titleabbrev>
 
@@ -47,7 +47,7 @@
 
  &reference.{EXT_NAME_ID}.entities.{CLASS_NAME_ID};
 
-</phpdoc:classref>
+</reference>
 <!-- Keep this comment at the end of the file
 Local variables:
 mode: sgml

scripts/docgen/docgen.php

@@ -90,7 +90,7 @@ function usage() { /* {{{ */
 }
 /* }}} */
 
-function find_function($ext, ReflectionMethod $method = NULL, ReflectionFunction $func = NULL) { /* {{{ */
+function find_function($ext, ?ReflectionMethod $method = NULL, ?ReflectionFunction $func = NULL) { /* {{{ */
 	$ext_name = strtolower($ext);
 	$ext = new ReflectionExtension($ext);
 
@@ -224,7 +224,7 @@ function get_type_by_string($str) { /* {{{ */
 /* }}} */
 
 /** @return string|null */
-function get_type_as_xml_string(ReflectionType $type = null) { /* {{{ */
+function get_type_as_xml_string(?ReflectionType $type = null) { /* {{{ */
 	if ($type instanceof ReflectionNamedType) {
 		$ret = "<type>{$type->getName()}</type>";
 		if ($type->allowsNull()) {