Replace the extremely poor drand48 with a proper one

[rurban]

Note that the perl5 design choices for drand48() are extremely poor. (but not entirely unexpected from p5p).

1st: Taking the primitive freebsd rand48() they use ldexp(.., -48)
to expand the 48 bits to a double, not the much faster bitmasking.
ldexp uses 5 branches and 1-2 multiplications. This is ~2x slower than needed.
The FreeBSD original is sane here, but even gsl is doing the same. Wonder who was first.

2nd: Masking to 48 bits not 53 makes creating uniform double values much harder.
Normally you would create 64-bit numbers as with every other rng. Then
you have proper int ranges as well as double.

Use a good one instead, which works on 32bit and 64bit systems,
producing full range ints and doubles, and much faster. e.g wyrand.
See https://rurban.github.io/dieharder/QUALITY.html (look for drand48 at the bottom).

And while we are here, seperate pp_rand into int and double methods.
It makes not much sense to produce costly doubles, when only int values are requested.

Already filed at #10, then I thought PCG or xoroshiro128+ would be best (before actually testing them)