This is in autoconf-provided shell code, so it will go away if
autoconf is ever re-run.

diff --git a/configure b/configure
index 7c61baff18e8b230..2c2e6d3513003592 100755
--- a/configure
+++ b/configure
@@ -2543,8 +2543,8 @@ main ()
   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