Now that mlockall(2) is unbroken, use it to keep watchdogd(8) permanently

out of swap.

usr.sbin/watchdogd/watchdogd.c

@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/rtprio.h>
 #include <sys/stat.h>
 #include <sys/time.h>
+#include <sys/mman.h>
 #include <sys/watchdog.h>
 
 #include <err.h>
@@ -87,6 +88,9 @@ main(int argc, char *argv[])
 	if (rtprio(RTP_SET, 0, &rtp) == -1)
 		err(EX_OSERR, "rtprio");
 
+	if (mlockall(MCL_CURRENT | MCL_FUTURE) == -1)
+		err(EX_OSERR, "mlockall");
+
 	if (watchdog_init() == -1)
 		errx(EX_SOFTWARE, "unable to initialize watchdog");