Expand globs to zero arguments (nullglob) only for set, for and count.
The warning about failing globs, and setting the accompanying $status,
now happens regardless of mode, interactive or not.
It is assumed that the above commands are the common cases where
nullglob behaviour is desirable.
More importantly, doing this with `set` is a real feature enabler,
since the resulting empty array can be passed on to any command.
The previous behaviour was actually all nullglob (since commit
cab115c8b9), but this was undocumented;
the failglob warning was still printed in interactive mode,
and the documentation was bragging about failglob behaviour.
