Avoid autom4te warning about unnamed diversion.

[Ralf Wildenhues]

I get this warning from recent Autoconf when bootstrapping Libtool:

$ ./bootstrap
[...]
autom4te --language=m4sh -B libltdl/config libltdl/config/ltmain.m4sh > 
libltdl/config/ltmain.in
libltdl/config/getopt.m4sh:1: warning: prefer named diversions

The patch below fixes it.  OK?

Thanks,
Ralf

   Avoid autom4te warning about unnamed diversion.

   * libltdl/config/getopt.m4sh: Use diversion name KILL not -1.

diff --git a/libltdl/config/getopt.m4sh b/libltdl/config/getopt.m4sh
index a81a905..27d2cd4 100644
--- a/libltdl/config/getopt.m4sh
+++ b/libltdl/config/getopt.m4sh
@@ -1,4 +1,4 @@
-m4_include([general.m4sh])m4_divert_push(-1)
+m4_include([general.m4sh])m4_divert_push(KILL)
 # getopt.m4sh -- getopt helper functions                -*- Autoconf -*-
 #
 #    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software 
Foundation, Inc.
@@ -496,7 +496,7 @@ m4go_validation
 # operation of the automatic `--version' and `--help' options, among
 # others.
 
-m4_divert_pop(-1)M4SH_VERBATIM([[
+m4_divert_pop(KILL)M4SH_VERBATIM([[
 # func_version
 # Echo version message to standard output and exit.
 func_version ()