Include <string.h> rather than <strings.h> for string function prototypes.

Approved by:	das (mentor)

usr.sbin/fdwrite/fdwrite.c

@@ -16,7 +16,7 @@
 #include <paths.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <strings.h>
+#include <string.h>
 #include <unistd.h>
 
 #include <sys/fdcio.h>

usr.sbin/mount_portalfs/pt_tcp.c

@@ -42,7 +42,7 @@ __FBSDID("$FreeBSD$");
 
 #include <errno.h>
 #include <stdlib.h>
-#include <strings.h>
+#include <string.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/param.h>

usr.sbin/mount_portalfs/pt_tcplisten.c

@@ -48,7 +48,7 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 #include <stdlib.h>
 #include <errno.h>
-#include <strings.h>
+#include <string.h>
 #include <sys/types.h>
 #include <sys/param.h>
 #include <sys/syslog.h>