Use PRNG from inkjs

[joethephish]

As mentioned in y-lohse/inkjs#31, make use of the nice simple custom PRNG implementation to be consistent between ink runtime implementations.

This is the reference implementation.

[Glidias]

The PRNG for haxe is similar,
https://github.com/Glidias/inkhaxe/blob/master/src/ink/random/ParkMiller.hx

except for....

other than the (%modulus seed check) being used (i guess this is needed for Javascript, since it's untyped..) , I wonder why the reference implementation has a -1 in return (this.next() - 1) / 2147483646; but there's no -1 for the haxe version i'm using.