AW: assignment command / status of RR

[Andreas.Eversberg]

> Using the scheduler should be relatively easy, you can simply call
> sched_gsmtime() and provide it a framenumber and a 'tdma_sched_item'.
the
> latter will contain the callback that is to be called once the current
> framenumber will reach 'fn' as specified.

what if there is already a scheduled item? in this case i must schedule
the frequency change item before any other item. also the frame number
of frequency change may be more than 255 frames ahead.

my suggestion: because hopping sequence is a function of time, the
starting time should also be included in this function (rfch.c).