Fix UNKNOWN default parameters of rand() and mt_rand()

[dtakken]

Squash some more UNKNOWN defaults.

[Girgias]

These blocks should come after ZPP and you need to make the function work with one argument now for this to work.

[nikic]

Please see #6026 (comment).

[dtakken]

Ah yes, of course. The mt_rand() function could previously not be called with a single argument. Now it can, and we want its behavior to be intuitive. The following call is a little problematic in that regard:

mt_rand(10)

This will not do what you expect from the looks of it. However, this can be solved by using named arguments:

mt_rand(max: 10)

Another option that crossed my mind is to have the two parameters swap positions and accept it when min > max (just like rand() does) for backward compatibility. Then the following things will all work as you would expect:

mt_rand()
mt_rand(10)
mt_rand(5, 10)
mt_rand(min: 5)

Getting rid of the UNKNOWN parameters is nice, but there are no perfect solutions to do it...

[nikic]

As I said before, I don't think we should change anything here. The use of UNKNOWN is okay for overloaded signatures like these.

[dtakken]

Ok, closing this PR.