sigaction signum range test

[Kevin Ryde]

        * scmsigs.c (scm_sigaction_for_thread): Correction to signum range
        test, avoids SCM_VECTOR_REF outside bounds of signal_handlers on
        calling "(sigaction NSIG)".

This is just an off-by-one, signum==NSIG is the only bad case.  You
can provoke it under electric fence with

        (sigaction NSIG)

I see the 1.6 has no such range check at all, perhaps it'd be a good
idea.

--- scmsigs.c.~1.78.~   2003-04-07 08:05:26.000000000 +1000
+++ scmsigs.c   2004-04-01 08:06:32.000000000 +1000
@@ -1,4 +1,4 @@
-/* Copyright (C) 1995,1996,1997,1998,1999,2000,2001, 2002 Free Software 
Foundation, Inc.
+/* Copyright (C) 1995,1996,1997,1998,1999,2000,2001, 2002, 2004 Free Software 
Foundation, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -299,7 +299,7 @@
   SCM old_handler;
 
   SCM_VALIDATE_INUM_COPY (1, signum, csig);
-  if (csig < 0 || csig > NSIG)
+  if (csig < 0 || csig >= NSIG)
     SCM_OUT_OF_RANGE (1, signum);
 #if defined(HAVE_SIGACTION)
 #if defined(SA_RESTART) && defined(HAVE_RESTARTABLE_SYSCALLS)