Actually increment counter inside random_symbol

@RudolfWeeber is currently looking at the statistical mechanics of the fluctuating LB and found a velocity bias. It turned out that this is due to all generated random numbers using the same key. Instead it should be incremented when generating multiple random numbers in the same kernel.

So in the generated code,

philox_float4(time_step, ctr_0, ctr_1, ctr_2, 0, 2, Dummy_38, Dummy_39, Dummy_40, Dummy_41);
philox_float4(time_step, ctr_0, ctr_1, ctr_2, 0, 2, Dummy_34, Dummy_35, Dummy_36, Dummy_37);
philox_float4(time_step, ctr_0, ctr_1, ctr_2, 0, 2, Dummy_30, Dummy_31, Dummy_32, Dummy_33);
philox_float4(time_step, ctr_0, ctr_1, ctr_2, 0, 2, Dummy_26, Dummy_27, Dummy_28, Dummy_29);

becomes

philox_float4(time_step, ctr_0, ctr_1, ctr_2, 3, 2, Dummy_38, Dummy_39, Dummy_40, Dummy_41);
philox_float4(time_step, ctr_0, ctr_1, ctr_2, 2, 2, Dummy_34, Dummy_35, Dummy_36, Dummy_37);
philox_float4(time_step, ctr_0, ctr_1, ctr_2, 1, 2, Dummy_30, Dummy_31, Dummy_32, Dummy_33);
philox_float4(time_step, ctr_0, ctr_1, ctr_2, 0, 2, Dummy_26, Dummy_27, Dummy_28, Dummy_29);