[Fractdev] atan2_bf() problem

Tim, It appears that atan2_bf() in bigflt.c isn't working correctly. This affects cmplxlog_bf() and thus ComplexPower_bf() in fractalb.c. This can be seen by starting up the manzpower fractal type and then switching to arbitrary precision math using debug=3200. I found this while I was coding the dividebrot5 fractal. In the case of the dividebrot5 fractal, Fractint locks up. With the manzpower fractal, an image is generated, but not the correct one. Jonathan