Include structseq.h in Python.h, and remove now-redundant includes in individual sources.
diff --git a/Include/Python.h b/Include/Python.h
index 6ca7a58..a49753f 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -98,6 +98,7 @@
 #include "descrobject.h"
 #include "warnings.h"
 #include "weakrefobject.h"
+#include "structseq.h"
 
 #include "codecs.h"
 #include "pyerrors.h"