Fix test which was not cloning the state

Cloning the state really ensure that we are not
modifying it when calling.
Reset normal generator when resetting the seed
Rename C functions that obtain Mersenne-Twister state

The existing functions for the state only return the Mersenne
Twister state, not the full state. I renamed them accordingly,
and create two Lua functions getRNGState and setRNGState which
for now only call them but will soon be more easily gather the
rest of the state.
Return normal generator state as well as MT state

Tests now pass :)