Fix syntax error in aclocal.m4

[jrisc]

The block argument of the AC_CACHE_VAL call ends before the if instruction can reach the corresponding fi one. This fi is definitely meant to be part of this block.

[greghudson]

Looking at the history, this mistake has been present since 2000. I think the only practical consequence is that the AC_CACHE_VAL cleanup rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext winds up being conditional upon $ac_cv_func_inet_ntop" = "yes". How did you notice it? (I will accept the patch, of course, but whether it gets a ticket and backport depends on whether it has a more significant practical consequence in some environment.)

[jrisc]

This problem was identified by Frédéric Bérat while testing the upcoming version 2.72 of Autoconf on the Fedora build of krb5.

The error message is:

checking for IPv6 compile-time support without -DINET6... ./configure: line 10559: syntax error near unexpected token `;;'
./configure: line 10559: `rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext ;;'