Remove LIBXML_XINCLUDE option from valid list of XMLDocument (#20907)

This option is only valid for pull parsers.

NEWS

@@ -9,6 +9,10 @@ PHP                                                                        NEWS
     needing to be present beforehand. (ndossche)
   . Added `clamp()`. (kylekatarnls, thinkverse)
 
+- DOM:
+  . Removed LIBXML_XINCLUDE from valid options for XMLDocument,
+    as it was a no-op. (ndossche)
+
 - Fileinfo:
   . Fixed bug GH-20679 (finfo_file() doesn't work on remote resources).
     (ndossche)

ext/dom/tests/modern/xml/XMLDocument_fromString_03.phpt

@@ -6,7 +6,7 @@ dom
 <?php
 
 $flags = [
-    LIBXML_RECOVER, LIBXML_NOENT, LIBXML_DTDLOAD, LIBXML_DTDATTR, LIBXML_DTDVALID, LIBXML_NOERROR, LIBXML_NOWARNING, LIBXML_NOBLANKS, LIBXML_XINCLUDE, LIBXML_NSCLEAN, LIBXML_NOCDATA, LIBXML_NONET, LIBXML_PEDANTIC, LIBXML_COMPACT, LIBXML_PARSEHUGE, LIBXML_BIGLINES
+    LIBXML_RECOVER, LIBXML_NOENT, LIBXML_DTDLOAD, LIBXML_DTDATTR, LIBXML_DTDVALID, LIBXML_NOERROR, LIBXML_NOWARNING, LIBXML_NOBLANKS, LIBXML_NSCLEAN, LIBXML_NOCDATA, LIBXML_NONET, LIBXML_PEDANTIC, LIBXML_COMPACT, LIBXML_PARSEHUGE, LIBXML_BIGLINES
 ];
 
 try {
@@ -37,4 +37,3 @@ bool(true)
 bool(true)
 bool(true)
 bool(true)
-bool(true)

ext/dom/xml_document.c

@@ -39,7 +39,6 @@ static bool check_options_validity(uint32_t arg_num, zend_long options)
 								  | XML_PARSE_NOERROR
 								  | XML_PARSE_NOWARNING
 								  | XML_PARSE_NOBLANKS
-								  | XML_PARSE_XINCLUDE
 								  | XML_PARSE_NSCLEAN
 								  | XML_PARSE_NOCDATA
 								  | XML_PARSE_NONET
@@ -60,7 +59,6 @@ static bool check_options_validity(uint32_t arg_num, zend_long options)
 										   "LIBXML_NOERROR, "
 										   "LIBXML_NOWARNING, "
 										   "LIBXML_NOBLANKS, "
-										   "LIBXML_XINCLUDE, "
 										   "LIBXML_NSCLEAN, "
 										   "LIBXML_NOCDATA, "
 										   "LIBXML_NONET, "