Core/Weather: defined new weather state entry found in Gilneas sniff

src/server/game/Weather/Weather.h

@@ -57,6 +57,7 @@ enum WeatherState : uint32
     WEATHER_STATE_MEDIUM_SANDSTORM  = 41,
     WEATHER_STATE_HEAVY_SANDSTORM   = 42,
     WEATHER_STATE_THUNDERS          = 86,
+    WEATHER_STATE_RAIN_DRIZZLE      = 87,
     WEATHER_STATE_BLACKRAIN         = 90,
     WEATHER_STATE_BLACKSNOW         = 106
 };