[msvc] Fix warnings, mainly casting to smaller types (#270)

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src/mbgl/gl/render_custom_layer.cpp

@@ -86,7 +86,7 @@ void RenderCustomLayer::render(PaintParameters& paintParameters) {
     parameters.latitude = state.getLatLng().latitude();
     parameters.longitude = state.getLatLng().longitude();
     parameters.zoom = state.getZoom();
-    parameters.bearing = -state.getBearing() * util::RAD2DEG;
+    parameters.bearing = -state.getBearing() * util::RAD2DEG_D;
     parameters.pitch = state.getPitch();
     parameters.fieldOfView = state.getFieldOfView();
     mat4 projMatrix;