2.12 migration tips

[hmaarrfk]

Just leaving this here, I've seen many feedstocks get hung up on the error handler not being declared const.

diff -ur a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
--- a/src/backend/utils/adt/xml.c	2023-11-06 17:04:27.000000000 -0500
+++ b/src/backend/utils/adt/xml.c	2023-12-03 21:01:12.452541626 -0500
@@ -123,7 +123,7 @@
 										   xmlParserCtxtPtr ctxt);
 static void xml_errsave(Node *escontext, PgXmlErrorContext *errcxt,
 						int sqlcode, const char *msg);
-static void xml_errorHandler(void *data, xmlErrorPtr error);
+static void xml_errorHandler(void *data, const xmlError *error);
 static int	errdetail_for_xml_code(int code);
 static void chopStringInfoNewlines(StringInfo str);
 static void appendStringInfoLineSeparator(StringInfo str);
@@ -2002,7 +2002,7 @@
  * Error handler for libxml errors and warnings
  */
 static void
-xml_errorHandler(void *data, xmlErrorPtr error)
+xml_errorHandler(void *data, const xmlError *error)
 {
 	PgXmlErrorContext *xmlerrcxt = (PgXmlErrorContext *) data;
 	xmlParserCtxtPtr ctxt = (xmlParserCtxtPtr) error->ctxt;