Milter-greylist

> > I am not an autoconf expert.
> > May anybody help to write the test for the existence of res_state?
> 
> Use existing tests. Add this to configure.ac:
> AC_CHECK_TYPE (res_state)
> 
> Run autoconf && autoheader && ./configure
> 
> config.h should have a HAVE_RES_STATE set or unset, depending whether
> configure found it or not. Check config.log to make sure the test did
> not fail for a missing header. (you may have to use AC_INCLUDES_DEFAULT
> in that case)
> 

Well, before adding the line
AC_CHECK_TYPE(res_state)
to the configure.ac I tested how the autoconf behaves.
When running autoconf (no modification relative to 4.5.7) I got the following:

configure.ac:94: error: possibly undefined macro: _AC_DEFINE_UNQUOTED
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.

Could you advise please?