Milter-greylist

Hi,

after migrating to a new OS with gcc version 7.4.0 (before version 4.8.5) 
I got a problem while building milter-greylist 4.6.2. If I use the 
configure option "--enable-dnsrbl" I got the error

  checking if DNS resolver is re-entrant... no
  --enable-dnsrbl used but DNS resolver is not thread safe
  Try installing BIND9 and using --with-libbind, or if you
  know what you are doing, use --with-thread-safe-resolver

Looking in the config.log I found

  configure:8280: checking if DNS resolver is re-entrant
  configure:8305: gcc -c -g -O2 -Wall -DHAVE_DATA_CALLBACK -Wall -Werror
  conftest.c >&5
  In file included from /usr/include/sys/types.h:25:0,
                   from conftest.c:71:
  /usr/include/features.h:183:3: error: #warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE" [-Werror=cpp]
   # warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE"
     ^~~~~~~
  cc1: all warnings being treated as errors

Ok, the generated test program uses

  #define _BSD_SOURCE

Although a testwise

  CFLAGS=-D_DEFAULT_SOURCE ./configure --enable-dnsrbl

seems also to work I changed simply in configure.ac, configure, 
Makefile.in and Makefile the string "_BSD_SOURCE" into "_DEFAULT_SOURCE" 
and now I got a

  checking if DNS resolver is re-entrant... yes

and could compile milter-greylist successfully.

Regards

Jens