rng.percent(-10) always return true

[Marcotte]

As written in the title: calling rng.percent() with a negative parameter always return true.

This is a little counterintuitive, as I expected that it would always return false for a negative parameter, and always true for a parameter higher than 100. And looking at the source code (core_lua.c line 1473), I have no idea why it is not the case.

[darkgod]

Weird indeed.
Some casting errors I suppose.

Fixed