adobe_coeff: Canon EOS 850D support

Author: cytrinox

src/external/adobe_coeff.c

@@ -61,6 +61,7 @@ static void dt_dcraw_adobe_coeff(const char *name, float cam_xyz[1][12])
     { "Canon EOS 750D", { 6362,-823,-847,-4426,12109,2616,-743,1857,5635 } },
     { "Canon EOS 760D", { 6362,-823,-847,-4426,12109,2616,-743,1857,5635 } },
     { "Canon EOS 800D", { 6970,-512,-968,-4425,12161,2553,-739,1982,5601 } },
+    { "Canon EOS 850D", { 9079,-1923,-1236,-4677,12454,2492,-922,2319,5565 } },
     { "Canon EOS 1000D", { 6771,-1139,-977,-7818,15123,2928,-1244,1437,7533 } },
     { "Canon EOS 1100D", { 6444,-904,-893,-4563,12308,2535,-903,2016,6728 } },
     { "Canon EOS 1200D", { 6461,-907,-882,-4300,12184,2378,-819,1944,5931 } },