Maxima incorrectly simplifies powers



Hello,

The following issue was reported to Sage.  Maxima currently simplifies
(x^2)^(1/3) to x^(2/3) which is not correct for all values of x.  For
example, ((-1)^2)^(1/3) correctly gives 1, but (-1)^(2/3) also gives 1
when it should give -1/2+sqrt(3)/2*I .

--Mike