Rework r296543:

Rework r296543:

1. Limit secs to INT32_MAX / 2 to avoid errors from kern_setitimer().
   Assert that kern_setitimer() returns 0.
   Remove bogus cast of secs.
   Fix style(9) issues.

2. Increment the return value if the remaining tv_usec value more than 500000 as a Linux does.

Pointed out by: [1] Bruce Evans

MFC after:	1 week