genesys: Don't use variants of M_PI that aren't guaranteed to be present

backend/genesys/conv.cpp

@@ -203,7 +203,7 @@ void genesys_deskew(Genesys_Scanner *s, const Genesys_Sensor& sensor)
                              sensor.optical_res, sensor.optical_res,
                              &x, &y, &slope));
 
-  DBG(DBG_info, "%s: slope=%f => %f\n",__func__,slope, (slope/M_PI_2)*90);
+    DBG(DBG_info, "%s: slope=%f => %f\n", __func__, slope, slope * 180 / M_PI);
 
     // rotate image slope is in [-PI/2,PI/2]. Positive values rotate trigonometric direction wise
     TIE(sanei_magic_rotate(&s->params, dev->img_buffer.data(),

backend/genesys/low.cpp

@@ -2421,7 +2421,8 @@ void sanei_genesys_load_lut(unsigned char* lut,
    * then take the tangent (T.O.A)
    * then multiply by the normal linear slope
    * because the table may not be square, i.e. 1024x256*/
-    rise = std::tan(static_cast<double>(slope) / 128 * M_PI_4 + M_PI_4) * max_out_val / max_in_val;
+    auto pi_4 = M_PI / 4.0;
+    rise = std::tan(static_cast<double>(slope) / 128 * pi_4 + pi_4) * max_out_val / max_in_val;
 
   /* line must stay vertically centered, so figure
    * out vertical offset at central input value */