time(1): kill some lint-era voids, switch to getprogname(3)

[Scott Cheloha]

The (void) casts are going out of style.  While here,
switch from __progname to getprogname(3)

--
Scott Cheloha

Index: usr.bin/time/time.c
===================================================================
RCS file: /cvs/src/usr.bin/time/time.c,v
retrieving revision 1.22
diff -u -p -r1.22 time.c
--- usr.bin/time/time.c 13 Jul 2017 06:39:54 -0000      1.22
+++ usr.bin/time/time.c 14 Jul 2017 00:34:33 -0000
@@ -93,8 +93,8 @@ main(int argc, char *argv[])
        }
 
        /* parent */
-       (void)signal(SIGINT, SIG_IGN);
-       (void)signal(SIGQUIT, SIG_IGN);
+       signal(SIGINT, SIG_IGN);
+       signal(SIGQUIT, SIG_IGN);
        while (wait3(&status, 0, &ru) != pid)
                ;
        clock_gettime(CLOCK_MONOTONIC, &after);
@@ -180,9 +180,7 @@ main(int argc, char *argv[])
 __dead void
 usage(void)
 {
-       extern char *__progname;
-
-       (void)fprintf(stderr, "usage: %s [-lp] utility [argument ...]\n",
-           __progname);
+       fprintf(stderr, "usage: %s [-lp] utility [argument ...]\n",
+           getprogname());
        exit(1);
 }