netstat: Use valid prototypes for function declarations with no arguments.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D39731

usr.bin/netstat/mroute.c

@@ -236,7 +236,7 @@ print_mfc(struct mfc *m, int maxvif, int *banner_printed)
 }
 
 void
-mroutepr()
+mroutepr(void)
 {
 	struct sockaddr_in sin;
 	struct sockaddr *sa = (struct sockaddr *)&sin;
@@ -411,7 +411,7 @@ mroutepr()
 }
 
 void
-mrt_stats()
+mrt_stats(void)
 {
 	struct mrtstat mrtstat;
 	u_long mstaddr;

usr.bin/netstat/mroute6.c

@@ -102,7 +102,7 @@ __FBSDID("$FreeBSD$");
 #define	WID_GRP	(Wflag ? 18 : (numeric_addr ? 16 : 18)) /* width of group column */
 
 void
-mroute6pr()
+mroute6pr(void)
 {
 	struct mf6c *mf6ctable[MF6CTBLSIZ], *mfcp;
 	struct mif6_sctl mif6table[MAXMIFS];
@@ -230,7 +230,7 @@ mroute6pr()
 }
 
 void
-mrt6_stats()
+mrt6_stats(void)
 {
 	struct mrt6stat mrtstat;