Changing field utmp.ut_time from int to time_t

This makes sure the types are coherent, and right now, time_t is
defined as an long, through _BSD_TIME_T_. It previously was
hardcoded as an int, so the structure's size does not change.

Change-Id: If29e94ab53f605d1480fadb540f5b67be4ddaf5b

include/utmp.h

@@ -75,7 +75,7 @@ struct utmp {
   char ut_host[UT_HOSTSIZE];		/* host name, when remote */
   short ut_pid;			/* process id */
   short int ut_type;		/* type of entry */
-  long ut_time;			/* login/logout time */
+  time_t ut_time;			/* login/logout time */
 };
 
 /* Definitions for ut_type. */