portability updates

add check if ipv6/sockaddr_in6 is availavble or not
add check for poll.h and only include when available
add includes for AROS

lib/iscsi-command.c

@@ -14,11 +14,20 @@
    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, see <http://www.gnu.org/licenses/>.
 */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+
+#ifdef HAVE_ARPA_INET_H
+#include <arpa/inet.h>
+#endif
 
 #if defined(WIN32)
 #include <winsock2.h>
-#else
-#include <arpa/inet.h>
 #endif
 
 #include <stdio.h>