Fix historic autoconf-generated checks to not fail with C99 compilers.

There is no need to upstream this patch because current autoconf no

longer generates these problematic checks.

diff --git a/configure b/configure

index f4812065f79460af..dfc195eb7d62840d 100755

--- a/configure

+++ b/configure

@@ -2098,7 +2098,7 @@ if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5

   echo "$as_me:$LINENO: \$? = $ac_status" >&5

   (exit $ac_status); }; }; then

   for ac_declaration in \

-   '' \

+   '#include <stdlib.h>' \

    'extern "C" void std::exit (int) throw (); using std::exit;' \

    'extern "C" void std::exit (int); using std::exit;' \

    'extern "C" void exit (int) throw ();' \

@@ -2759,8 +2759,8 @@ 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