Unify the time handling

Some options are in seconds, if no units are given. These include
runtime/timeout, startdelay, and ramp_time. Handle this
appropriately. Internally it should all be microseconds now, it's
just the conversion factor.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/time.h b/time.h
index d835191..c550a55 100644
--- a/time.h
+++ b/time.h
@@ -7,6 +7,7 @@
 extern uint64_t mtime_since_now(struct timeval *);
 extern uint64_t time_since_now(struct timeval *);
 extern uint64_t mtime_since_genesis(void);
+extern uint64_t utime_since_genesis(void);
 extern void usec_spin(unsigned int);
 extern void usec_sleep(struct thread_data *, unsigned long);
 extern void fill_start_time(struct timeval *);