Explicit template instantiations for mixins for value classes

To reduce compile time.

src/blackmisc/weather/temperaturelayer.cpp

@@ -12,6 +12,8 @@
 using namespace BlackMisc::Aviation;
 using namespace BlackMisc::PhysicalQuantities;
 
+BLACK_DEFINE_VALUEOBJECT_MIXINS(BlackMisc::Weather, CTemperatureLayer)
+
 namespace BlackMisc::Weather
 {