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/source/ecs_utils/gfx/renderer.d

@@ -12,6 +12,7 @@ import ecs_utils.math.vector;
 import bubel.ecs.block_allocator;
 import bubel.ecs.vector;
 version(WebAssembly)import glad.gl.gles2;
+else version(Android)import glad.gl.gles2;
 else import glad.gl.gl;
 
 version = ver1;
@@ -637,6 +638,7 @@ struct Renderer
             if(threads[thread_id].block.items >= VertexBlock.max_items)
             {
                 //pushBlock(threads[thread_id].block);
+                prepared_items += threads[thread_id].block.items;
                 threads[thread_id].blocks.add(threads[thread_id].block);
                 threads[thread_id].block = getBlock();
             }
@@ -667,6 +669,10 @@ struct Renderer
         {
             glDepthRangef(0,1);
         }
+        else version(Android)
+        {
+            glDepthRangef(0,1);
+        }
         else
         {
             glDepthRange(0,1);