Add missing #include <stddef.h> for offsetof when using -builtin.

Fixes SF #1345

CHANGES.current

@@ -5,6 +5,9 @@ See the RELEASENOTES file for a summary of changes in each release.
 Version 3.0.0 (in progress)
 ============================
 
+2013-10-17: wsfulton
+            [Python] Fix SF #1345 - Missing #include <stddef.h> for offsetof when using -builtin.
+
 2013-10-15: vadz
             Allow using \l, \L, \u, \U and \E in the substitution part of %(regex:/pattern/subst/)
             inside %rename to change the case of the text being replaced.

Lib/python/pyinit.swg

@@ -4,6 +4,10 @@
 
 %insert(init) "swiginit.swg"
 
+#if defined(SWIGPYTHON_BUILTIN)
+%fragment("<stddef.h>"); // For offsetof
+#endif
+
 %init %{
 
 #ifdef __cplusplus