[ntar-workers] Why is there an "end of options list" option?

[Guy Harris]

As the option list is always at the end of the block, the length of  
the option list should always be the length of the block, minus 8  
(for the block length and type), minus the length of stuff before the  
option list.

You have to check to make sure you don't run past the end of the  
block in any case - there's no guarantee that a given block will be  
valid, so there's no guarantee that there's an end-of-options option  
before the end of the block - so it'd be simpler to have the loop  
that processes options just check to see whether there are any bytes  
of option left.