Fix error in randomInt with large Ints

[moogle19]

The initialisation of the UInt32 in randomInt failed, when max - min + 1 was bigger than UInt32.max.
This can happen because Int is a Int64 on 64-bit systems.

I replaced arc4random_uniform with arc4random_buf which just fills the Int with random bits.

To transform the random number to a positive one, I used & Int.max to set the first bit to 0 (which is faster than abs())

[moogle19]

The second commit adds a check for the range between max and min. When this is bigger than Int.max, then max - min fails (because it gets too big).
I simply check if max is bigger than 0 and if max - Int.max is bigger than min. Then we don't need to cap the random number.

[vadymmarkov]

@moogle19 Thanks 👍