GNU/Hurd doesn't have EBADE.  Report EGRATUITOUS there for now (or EIO on any
other system which doesn't have EBADE either).

Index: oss4-4.2-build2004/lib/libsalsa/seq_output.c
===================================================================
--- oss4-4.2-build2004.orig/lib/libsalsa/seq_output.c	2011-06-14 11:33:24.000000000 -0500
+++ oss4-4.2-build2004/lib/libsalsa/seq_output.c	2011-06-14 11:33:24.000000000 -0500
@@ -40,7 +40,13 @@
       if (l == -1)
 	return -errno;
 
+#ifdef EBADE
       return -EBADE;		/* Randomly selected error */
+#elif defined(EGRATUITOUS)
+      return -EGRATUITOUS;	/* Randomly selected error */
+#else
+      return -EIO;		/* Randomly selected error */
+#endif
     }
 
   return 0;
@@ -65,7 +71,13 @@
       if (l == -1)
 	return -errno;
 
+#ifdef EBADE
       return -EBADE;		/* Randomly selected error */
+#elif defined(EGRATUITOUS)
+      return -EGRATUITOUS;	/* Randomly selected error */
+#else
+      return -EIO;		/* Randomly selected error */
+#endif
     }
 
   return 0;