Added WELL in 64 bits.

This commit only has the code for the
64-bits version of WELL, the explanation
of how it is done should come soon.
But, it involves calculating in parallel
two 32 numbers ;)
Have forgotten that the status are pointers
instead of structures (. to ->)
Changed the seed functions to WELL 64-bits

Seems that rand() only returns 32 bits although
you ask 64 to it...