Manually specify the number of values to unpack

[SquidDev]

table.unpack will often stop at the first nil value, meaning some event arguments may be discarded. By storing the number of arguments through table.pack, and then using that count when unpacking, we can ensure all values are returned/resumed with.

This can be seen by running the following script:

os.queueEvent("foo", 1, nil, 2)
print(os.pullEvent("foo"))

Without this patch it will print foo 1. With it you get foo 1 nil 2 as expected. There was also an Ask a Pro issue with someone sending a nil rednet message, resulting in the protocol being nil.

Note I haven't patched any of the rom files (such as nsh) as that might be better left for their respective authors. I also haven't touched anything which deals with command line arguments - those should never be nil anyway. I'm happy to change them too, should people wish.