I've just updated to the latest master and get this error when compiling on Solaris 11 with gcc version 4.5.2:
LD (gcc) [kamailio]             kamailio
Undefined                       first referenced
 symbol                             in file
gethostbyname2                      dns_func.o
ld: fatal: symbol referencing errors. No output written to kamailio
collect2: ld returned 1 exit status
gmake: *** [kamailio] Error 1

In Makefile.defs Solaris does not define HAVE_GETHOSTBYNAME2.

I fixed this by putting #ifdef HAVE_GETHOSTBYNAME2 around all gethostbyname2 in:
dns_func.c
dns_func.h
modules/dnssec/dnssec_func.c
modules/dnssec/dnssec_func.h
modules/dnssec/dnssec_mod.c