Clean up warnings that can use the _unused macro

X-Gentoo-Bug: 604666
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=604666

src/rc/supervise-daemon.c

@@ -62,6 +62,7 @@ static struct pam_conv conv = { NULL, NULL};
 #include "rc.h"
 #include "rc-misc.h"
 #include "_usage.h"
+#include "helpers.h"
 
 const char *applet = NULL;
 const char *extraopts = NULL;
@@ -124,7 +125,8 @@ extern char **environ;
 # define SYS_ioprio_set __NR_ioprio_set
 #endif
 #if !defined(__DragonFly__)
-static inline int ioprio_set(int which, int who, int ioprio)
+static inline int ioprio_set(int which _unused, int who _unused,
+			     int ioprio _unused)
 {
 #ifdef SYS_ioprio_set
 	return syscall(SYS_ioprio_set, which, who, ioprio);