Windows: Fix Narrowing conversion of seed in MaxPointCount

[maxGimeno]

Fix #469

[ethzasl-jenkins]

Can one of the admins verify this patch?

[lrineau]

The constructor of std::minstd_rand expects a std::uint_fast32_t as first argument.

• On a x86_64 Linux machine, that type is an unsigned long int, and thus a 64 bits unsigned.
• It seems that on Windows with the compiler from MSVC, that type is unsigned int, and thus only a 32 bits integer.

And thus on Windows, passing seed to that std::uint_fast32_t argument is a narrowing conversion. As the constructor was called with {seed} and not (seed), that narrowing conversion triggered an error.

[pomerlef]

Ok to test

[pomerlef]

Thanks!