introduced the Error class to represent an error code as an object.

rewrote STIX_ASSERT() to call stix_logbfmt() via stix_assertfailed()

stix/kernel/Apex.st

@@ -332,4 +332,10 @@
 	}
 }
 
-
+#class Error(Apex)
+{
+	#method isError
+	{
+		^true
+	}
+}