maxima - differentiate works incorrect

[Lukas Neumann]

Hi,
Maxima-5.9.0p1 (_3_9) - "diff(sin(x),x);" doesnt returns the result 
"cos(x)", only the function. Its a known problem in 5.9.0.
5.9.1 return the correct results for "diff". Perhaps you could update it 
in _CURRENT.

grx
Lukas