restore namespacing of pyexpat symbols (closes #19186)

Misc/NEWS

@@ -45,6 +45,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #19186: Restore namespacing of expat symbols inside the pyexpat module.
+
 - Issue #20426: When passing the re.DEBUG flag, re.compile() displays the
   debug output every time it is called, regardless of the compilation cache.
 

Modules/expat/expat_external.h

@@ -7,6 +7,10 @@
 
 /* External API definitions */
 
+/* Namespace external symbols to allow multiple libexpat version to
+   co-exist. */
+#include "pyexpatns.h"
+
 #if defined(_MSC_EXTENSIONS) && !defined(__BEOS__) && !defined(__CYGWIN__)
 #define XML_USE_MSC_EXTENSIONS 1
 #endif