Include <sys/types.h> in the PCAP_IS_SUITABLE test.

The lack of this was causing PCAP_IS_SUITABLE to fail on Arch Linux, at
least. I think that in some cases this caused both -L../libpcap and
-lpcap to be added to the linker line, which could cause an error
because of the need to link with -lnl. (We check for -lnl when
--with-libpcap=included is used (since r23163), but the PCAP_IS_SUITABLE
failure went around this check and allowed linking with the included
libpcap without checking whether -lnl is required.)

Here are reported build failures and responses:
http://seclists.org/nmap-dev/2011/q3/449
http://seclists.org/nmap-dev/2011/q4/33
http://seclists.org/nmap-dev/2012/q1/369

acinclude.m4

@@ -51,6 +51,7 @@ int main() {
   ], [
     AC_TRY_RUN([
 #include <stdio.h>
+#include <sys/types.h>
 #ifdef HAVE_SYS_IOCCOM_H
 #include <sys/ioccom.h>
 #endif

configure

@@ -6293,6 +6293,7 @@ else
 /* end confdefs.h.  */
 
 #include <stdio.h>
+#include <sys/types.h>
 #ifdef HAVE_SYS_IOCCOM_H
 #include <sys/ioccom.h>
 #endif

ncat/configure

@@ -4814,6 +4814,7 @@ else
 /* end confdefs.h.  */
 
 #include <stdio.h>
+#include <sys/types.h>
 #ifdef HAVE_SYS_IOCCOM_H
 #include <sys/ioccom.h>
 #endif

nping/configure

@@ -5254,6 +5254,7 @@ else
 /* end confdefs.h.  */
 
 #include <stdio.h>
+#include <sys/types.h>
 #ifdef HAVE_SYS_IOCCOM_H
 #include <sys/ioccom.h>
 #endif