This a fix to autoconf-generated code.  No need to upstream this because
current autoconf does not generate it anymore.

diff -ur greyhounds-0.8-pre-alpha.orig/configure greyhounds-0.8-pre-alpha/configure
--- greyhounds-0.8-pre-alpha.orig/configure	2003-12-14 18:38:58.000000000 +0100
+++ greyhounds-0.8-pre-alpha/configure	2022-11-27 17:21:47.041164505 +0100
@@ -4061,8 +4061,8 @@
   for (i = 0; i < 256; i++)
     if (XOR (islower (i), ISLOWER (i))
 	|| toupper (i) != TOUPPER (i))
-      exit(2);
-  exit (0);
+      return 2;
+  return 0;
 }
 _ACEOF
 rm -f conftest$ac_exeext