Fix phpGH-17847: xinclude destroys live node

dom_xinclude_strip_fallback_references() now also takes into account
xi:include nodes children. This now subsumes all work done normally by
the old start/end node removal, so we can remove that code and start
using XML_PARSE_NOXINCNODE.

Closes phpGH-17878.

Author: nielsdos

NEWS

@@ -16,6 +16,9 @@ PHP                                                                        NEWS
   . Fixed bug GH-17797 (zend_test_compile_string crash on invalid
     script path). (David Carlier)
 
+- DOM:
+  . Fixed bug GH-17847 (xinclude destroys live node). (nielsdos)
+
 - FFI:
   . Fix FFI Parsing of Pointer Declaration Lists. (davnotdev)