Batch of lightmapper fixes and minor improvements

- Fix objects with no material being considered as fully transparent by the lightmapper.
- Added "environment_min_light" property: gives artistic control over the shadow color.
- Fixed "Custom Color" environment mode, it was ignored before.
- Added "interior" property to BakedLightmapData: controls whether dynamic capture objects receive environment light or not.
- Automatically update dynamic capture objects when the capture data changes (also works for "energy" which used to require object movement to trigger the update).
- Added "use_in_baked_light" property to GridMap: controls whether the GridMap will be included in BakedLightmap bakes.
- Set "flush zero" and "denormal zero" mode for SSE2 instructions in the Embree raycaster. According to Embree docs it should give a performance improvement.

modules/raycast/lightmap_raycaster.cpp

@@ -33,6 +33,7 @@
 // From Embree.
 #include <math/vec2.h>
 #include <math/vec3.h>
+#include <xmmintrin.h>
 
 using namespace embree;
 
@@ -185,12 +186,18 @@ void embree_error_handler(void *p_user_data, RTCError p_code, const char *p_str)
 }
 
 LightmapRaycasterEmbree::LightmapRaycasterEmbree() {
+	_MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_ON);
+	_MM_SET_DENORMALS_ZERO_MODE(_MM_DENORMALS_ZERO_ON);
+
 	embree_device = rtcNewDevice(nullptr);
 	rtcSetDeviceErrorFunction(embree_device, &embree_error_handler, nullptr);
 	embree_scene = rtcNewScene(embree_device);
 }
 
 LightmapRaycasterEmbree::~LightmapRaycasterEmbree() {
+	_MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_OFF);
+	_MM_SET_DENORMALS_ZERO_MODE(_MM_DENORMALS_ZERO_OFF);
+
 	if (embree_scene != nullptr)
 		rtcReleaseScene(embree_scene);
 	if (embree_device != nullptr)