New functions: jiffies() and uptime(), implemented with sysinfo()

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/util.h

@@ -40,6 +40,10 @@ extern char *prognm;
 
 char *progname     (char *arg0);
 void  do_sleep     (unsigned int sec);
+
+long  jiffies      (void);
+char *uptime       (long secs, char *buf, size_t len);
+
 char *sanitize     (char *arg, size_t len);
 
 void  screen_init  (void);