Add a couple of extra unistd.h includes to fix a build failure

src/iosource/BPF_Program.cc

@@ -1,12 +1,11 @@
 // See the file "COPYING" in the main distribution directory for copyright.
 
-#include <unistd.h>
-#include <sys/socket.h>
-
 #include "zeek/iosource/BPF_Program.h"
 
 #include "zeek/zeek-config.h"
 
+#include <unistd.h>
+#include <sys/socket.h>
 #include <cstring>
 
 #include "zeek/util.h"

src/iosource/pcap/Dumper.h

@@ -2,6 +2,8 @@
 
 #pragma once
 
+#include <unistd.h>
+
 extern "C"
 	{
 #include <pcap.h>

src/iosource/pcap/Source.h

@@ -3,6 +3,7 @@
 #pragma once
 
 #include <sys/types.h> // for u_char
+#include <unistd.h>
 
 extern "C"
 	{