package/cegui: fix build with libxml2 >= 2.12

Fix the following build failure raised since bump of libxml2 to version
2.12.1 in commit d8ac52108c12f0fcc9641b63e7922009270f96c6:

/home/buildroot/autobuild/instance-1/output-1/build/cegui-00b4e1fe174da53b7ed726ab5970ba51bd5b5ee0/cegui/src/XMLParserModules/Libxml2/XMLParser.cpp: In member function 'virtual void CEGUI::LibxmlParser::parseXML(CEGUI::XMLHandler&, const CEGUI::RawDataContainer&, const CEGUI::String&, bool)':
/home/buildroot/autobuild/instance-1/output-1/build/cegui-00b4e1fe174da53b7ed726ab5970ba51bd5b5ee0/cegui/src/XMLParserModules/Libxml2/XMLParser.cpp:111:40: error: invalid conversion from 'const xmlError*' {aka 'const _xmlError*'} to 'xmlError*' {aka '_xmlError*'} [-fpermissive]
  111 |         xmlError* err = xmlGetLastError();
      |                         ~~~~~~~~~~~~~~~^~
      |                                        |
      |                                        const xmlError* {aka const _xmlError*}

Fixes: d8ac52108c12f0fcc9641b63e7922009270f96c6
 - http://autobuild.buildroot.org/results/b239b7b03542311e311e4612e9b811c154302a6e

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/cegui/0002-Fix-return-type-of-xmlGetLastError-for-libxml2-2-12.patch

@@ -0,0 +1,29 @@
+From 285ba5a2c0c435ed865c6e86afe314a822fd1e3f Mon Sep 17 00:00:00 2001
+From: oreo639 <oreo6391@gmail.com>
+Date: Sun, 18 Feb 2024 14:16:21 -0800
+Subject: [PATCH] Fix return type of xmlGetLastError for libxml2 2.12
+
+https://gitlab.gnome.org/GNOME/libxml2/-/commit/45470611b047db78106dcb2fdbd4164163c15ab7
+
+Upstream: https://github.com/cegui/cegui/commit/285ba5a2c0c435ed865c6e86afe314a822fd1e3f
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ cegui/src/XMLParserModules/Libxml2/XMLParser.cpp | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/cegui/src/XMLParserModules/Libxml2/XMLParser.cpp b/cegui/src/XMLParserModules/Libxml2/XMLParser.cpp
+index 74a3dbddd..a408f9305 100644
+--- a/cegui/src/XMLParserModules/Libxml2/XMLParser.cpp
++++ b/cegui/src/XMLParserModules/Libxml2/XMLParser.cpp
+@@ -109,7 +109,11 @@ void LibxmlParser::parseXML(XMLHandler& handler,
+ 
+     if (!doc)
+     {
++#if LIBXML_VERSION >= 21200
++        const xmlError* err = xmlGetLastError();
++#else
+         xmlError* err = xmlGetLastError();
++#endif
+ 
+         throw GenericException(
+             String("xmlParseMemory failed in file: '") +