fix setting cells of normals in dw_surface_v_dot_n_s(), dw_surface_s_v_dot_n()
fix setting cells of normals in dw_surface_v_dot_n_s(), dw_surface_s_v_dot_n()

rc/sfepy,sfepy/sfepy,BubuLK/sfepy,sfepy/sfepy,RexFuzzle/sfepy,vlukes/sfepy,RexFuzzle/sfepy,RexFuzzle/sfepy,rc/sfepy,lokik/sfepy,RexFuzzle/sfepy,lokik/sfepy,lokik/sfepy,BubuLK/sfepy,sfepy/sfepy,vlukes/sfepy,lokik/sfepy,vlukes/sfepy,BubuLK/sfepy,rc/sfepy