Autoconf 2.50 breakage

[Igor Khavkine]

Hi, I contribute to GNU/Hurd development and have recently run into a
problem when I upgraded to autoconf-2.50. Turns out our aclocal.m4 file
uses macros that were deprecated in the new release of autoconf.
Namely AC_PROG_CC_GNU and AC_TRY_COMPILER, AC_PROG_CC_LOCAL uses
them.

After a discussion with Roland McGrath, he noted that glibc uses
the same macros and thus will run into problems when trying to
regenerate the configure script using the new autoconf. 
I gave it a shot on my glibc tree, and it turns out that the
situation is even worse. Autoconf fails with a fatal error:

./aclocal.m4:6: error: m4_defn: undefined: _m4_divert_diversion
acgeneral.m4:703: AC_FD_MSG is expanded from...
./aclocal.m4:6: the top level

Since parts out our aclocal.m4 file were originally taken from
glibc, we want to see if and how you're going to address
the problem.

Thanks.

Igor