`sleep`: Suspend Execution for an Interval

The subroutine is called by:

`call sleep(` `itime` `)`
`itime`	`INTEGER*4`	Input	Number of seconds to sleep

The actual time can be up to 1 second less than itime due to granularity in system timekeeping.

Example: sleep():

    INTEGER*4 time / 5 /
    write(*,*) 'Start'
    call sleep( time )
    write(*,*) 'End'
    end

sleep: Suspend Execution for an Interval