mpz_ui_pow_ui function on 64 bit machine

[Randall]

Hello all:

Something I noticed just today, perhaps just only on my Athlon64 machine.

Apparently the mpz_ui_pow_ui(ROP, ui base, ui power) function isn't working 
quite right for base being a 64 bit long integer.  It works okay for a 32 bit 
integer.  I was forced to change my base to 32 bit integers machine type.

Could someone please check into this?  I am not sure if this is just a one 
time occurance for my machine only.  Of course, gmp has been compiled with 
the -mtune=athlon64 option, which is the legitimate gcc target for my 
motherboard.

- Randall