Correct a spelling error flagged by lintian

Author: Peter Drysdale <drysdalepete@gmail.com>

Forwarded: https://github.com/festvox/speech_tools/pull/4

Applied-Upstream: https://github.com/festvox/speech_tools/pull/4/commits/3d03c8ad98f0dad56e4064b70c5715b4f494fbfb

--- a/siod/slib.cc

+++ b/siod/slib.cc

@@ -626,7 +626,7 @@

 void err_stack(char *ptr)

      /* The user could be given an option to continue here */

 {(void)ptr;

- err("the currently assigned stack limit has been exceded",NIL);}

+ err("the currently assigned stack limit has been exceeded",NIL);}

 LISP stack_limit(LISP amount,LISP silent)

 {if NNULLP(amount)