Android update and small improvements

-fixed code do cross compiling to android
-fixed build with GCC (workaround)
-added little benchmark
-several small fixes
-updated meson build (demos building, working with GCC, LDC and DMD)
-added some meson options
-added ImGUI bind for OpenGL3

demos/utils/dub.json

@@ -15,14 +15,13 @@
 		"../external/sources"
 	],
 	"dependencies": {
-		"bindbc-sdl":"0.13.0",
+		"bindbc-sdl":"0.19.0",
 		"ecs":{"path":"../../"}
 	},
 	"versions": [
 		"BindSDL_Image",
 		"SDL_2010"
 	],
-	
 	"configurations" : [
 		{
 			"name" : "default",