AC_DIAGNOSE not obsolete, please

[Karl Berry]

Zack and all - Thien-Thi (cc'd) just reported two failures in automake
make check with autoconf-2.69c (bugs.gnu.org/43819). The critical
message appears to be:

    ./lib/autoconf/general.m4:2328: AC_DIAGNOSE is expanded from...
    /home/ttn/local/.b/automake-1.16.2/m4/init.m4:29: AM_INIT_AUTOMAKE is 
expanded from...
    configure.ac:2: the top level
    configure.ac:2: warning: The macro `AC_DIAGNOSE' is obsolete.

Since AM_INIT_AUTOMAKE calls AC_DIAGNOSE, can you please not make
it obsolete? Otherwise upgrading will be a nightmare for everyone.

(Personally I'm skeptical that any longstanding macro should ever be
declared obsolete. But anyway.)

Thanks,
Karl