Needed to get the alloca() declaration.

--- hplip-3.25.6/pcard/pcardext/pcardext.c.orig
+++ hplip-3.25.6/pcard/pcardext/pcardext.c
@@ -39,6 +39,7 @@
 
 #include <Python.h>
 #include <structmember.h>
+#include <alloca.h>
 #include "../fat.h"
 
 /* Ref: PEP 353 (Python 2.5) */