Allow scm to build on OpenBSD/hppa.

--- setjump.h.orig	Sat Sep 25 22:48:58 2010
+++ setjump.h	Sat Sep 25 22:49:38 2010
@@ -123,3 +123,7 @@ typedef struct safeport {
 } safeport;
 
 #define SAFEP_JMPBUF(sfp) (((safeport *)STREAM(sfp))->jmpbuf)
+
+#if defined(__OpenBSD__) && defined(__hppa__)
+#define STACK_GROWS_UP
+#endif