[Chicken-users] remove enable/disable interrupt flag

[Alan Post]

This patch removes the enable/disable interrupt flag from the
scheduled.

I can't see that this code is referenced.  I'm not sure someone
would just write this feature for fun, however.  Is this code
actually used?

I'm preparing a larger patch for the signal handling code, so
knowing whether this is used (and how) is important for getting
my next set of patches correct.

-Alan
-- 
.i ma'a lo bradi cu penmi gi'e du