Cosmetic/consistency in Argon2i

Cosmetic/consistency in Argon2i

The functions g_copy() and g_xor() both take a pointer to a temporary,
to avoid wiping them again and again. unary_g(), however, did not, and
instead managed its temporary block internally.

Since unary_g() is called less often, this is not really a problem. I
thought it would be cleaner however to have all three functions work the
same way.

This should have a negligible, positive impact on performance as well.