Autoconf older than 2.63b (such as what ships on CentOS 6) had
a bug that any AC_DEFUN'd macro name that includes shell meta-
characters causes failure due to missing shell quoting during
aclocal's use of autom4te. We can work around the problem by
using m4_defun instead (same semantics in autom4te, but no
longer traced by aclocal, so no longer tickles the shell
quoting bug).
* m4/warnings.m4 (gl_UNKNOWN_WARNINGS_ARE_ERRORS(C))
(gl_UNKNOWN_WARNINGS_ARE_ERRORS(C++)): Use m4_defun rather than
AC_DEFUN.
* m4/manywarnings.m4 (gl_MANYWARN_ALL_GCC(C))
(gl_MANYWARN_ALL_GCC(C++)): Likewise.
Reported-by: Erik Skultety <eskultet@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com>