Would not build on Linux without including stddef.h before
including external.h.
diff --git a/expat/lib/xmlrole.c b/expat/lib/xmlrole.c
index 70c39f9..67b5eb5 100644
--- a/expat/lib/xmlrole.c
+++ b/expat/lib/xmlrole.c
@@ -2,6 +2,8 @@
    See the file COPYING for copying permission.
 */
 
+#include <stddef.h>
+
 #ifdef COMPILED_FROM_DSP
 #include "winconfig.h"
 #elif defined(MACOS_CLASSIC)
diff --git a/expat/lib/xmltok.c b/expat/lib/xmltok.c
index 2a967e2..4931a0c 100644
--- a/expat/lib/xmltok.c
+++ b/expat/lib/xmltok.c
@@ -2,6 +2,8 @@
    See the file COPYING for copying permission.
 */
 
+#include <stddef.h>
+
 #ifdef COMPILED_FROM_DSP
 #include "winconfig.h"
 #elif defined(MACOS_CLASSIC)