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

source/bubel/ecs/id_manager.d

@@ -15,7 +15,7 @@ struct IDManager
     /************************************************************************************************************************
     Get new ID.
     */
-    pragma(inline, false) EntityID getNewID() nothrow @nogc
+    EntityID getNewID() nothrow @nogc
     {
         int current = m_stack_top.atomicOp!"-="(1) + 1;
         if (current < 0)