The source you provided does compile (after an #include and creating a global int for slaveselect) on my 1.0 but as I have no ad9835 I connet test it further.
The source code i uploaded was is the arduino code. for raspberry pi i removed the # define SlaveSelectPin, actually it does not make a difference because the slaveselect pin is fixed on the pi.
Even I thought the ardupi may have some bugs. but i tested it for other basic SPI, and SPI works fine!
I have used a npn transistor as inverter to get the original MOSI signal back and the signal now is correct. Now i am getting correct signals of MOSI,SCLK,SS. So basically all signals are as required, but still no ouput. I am guessing the problem might be with the frequency of SPI. will try all permutations and combinations. Hope it works. Will update,