Unbreak build with libxml >=2.12.0

Index: src/object/uri.h
--- src/object/uri.h.orig
+++ src/object/uri.h
@@ -13,6 +13,7 @@
 #define INKSCAPE_URI_H
 
 #include <libxml/uri.h>
+#include <libxml/xmlmemory.h>
 #include <memory>
 #include <string>
 
