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/source/app.d

@@ -203,12 +203,10 @@ void mainLoop(void* arg)
         temp_fps = 0;
     }
 
-
     SDL_Event event;
     while (SDL_PollEvent(&event)) 
     {
-        version(WebAssembly)ImGui_ImplSDL2_ProcessEvent(&event);
-        else ImGui_ImplSDL2_ProcessEvent(&event);
+        ImGui_ImplSDL2_ProcessEvent(&event);
         if(launcher.event)launcher.event(&event);
         if (event.type == SDL_QUIT || (event.type == SDL_KEYDOWN && event.key.keysym.scancode == SDL_SCANCODE_ESCAPE)) {
             quit();
@@ -278,7 +276,8 @@ void mainLoop(void* arg)
     }
     else
     {
-        ImGuiImplOpenGL2NewFrame();
+        //ImGuiImplOpenGL2NewFrame();
+        ImGui_ImplOpenGL3_NewFrame();
         ImGuiImplSDL2NewFrame(launcher.window);
     }
 
@@ -632,7 +631,9 @@ void mainLoop(void* arg)
 
     igRender();
     version(WebAssembly)ImGui_ImplOpenGL3_RenderDrawData(igGetDrawData());
-    else ImGuiImplOpenGL2RenderDrawData(igGetDrawData());
+    else version(Android)ImGui_ImplOpenGL3_RenderDrawData(igGetDrawData());
+    else ImGui_ImplOpenGL3_RenderDrawData(igGetDrawData());
+    //ImGuiImplOpenGL2RenderDrawData(igGetDrawData());
     
     //launcher.renderer.clear();
     //launcher.renderer.present();
@@ -652,15 +653,48 @@ void quit()
     version(WebAssembly)emscripten_cancel_main_loop();
 }
 
-int main(int argc, char** argv)
+version(Android)
 {
+    export extern (C) int SDL_main(int argc, char** args)
+    {	
+        return app_main(argc,args);
+    }
+
+    import ldc.attributes;
+
+    extern (C) __gshared
+    {
+        @section(".tdata")
+        int _tlsstart = 0;
+        @section(".tcommon")
+        int _tlsend = 0;
+    }
+
+}
+else 
+{
+    extern (C) int main(int argc, char** argv)
+    {	
+        return app_main(argc,argv);
+    }
+}
+
+int app_main(int argc, char** argv)
+//int main(int argc, char** argv)
+{
+
+    version(BindSDL_Static){}
+    else 
+    {
+        loadSDL();
+        loadSDLImage();
+    }
 
     if (SDL_Init(SDL_INIT_VIDEO) < 0)
     {
         printf("SDL could not initialize! SDL_Error: %s", SDL_GetError());
         return -1;
     }
-
     SDL_version sdl_version;
     SDL_GetVersion(&sdl_version);
     printf("SDL version: %u.%u.%u\n",cast(uint)sdl_version.major,cast(uint)sdl_version.minor,cast(uint)sdl_version.patch);
@@ -692,6 +726,21 @@ int main(int argc, char** argv)
             return -3;
         }
     }
+    else version(Android)
+    {
+        //gladLoadGL();
+        gladLoadGLES2(x => SDL_GL_GetProcAddress(x));
+        if(!ImGuiImplSDL2InitForOpenGL(launcher.window,launcher.gl_context))
+        {
+            printf("ImGui initialization failed!");
+            return -2;
+        }
+        if(!ImGui_ImplOpenGL3_Init("#version 100"))
+        {
+            printf("ImGui OpenGL initialization failed!");
+            return -3;
+        }
+    }
     else 
     {
         gladLoadGL();
@@ -700,13 +749,14 @@ int main(int argc, char** argv)
             printf("ImGui initialization failed!");
             return -2;
         }
-        if(!ImGuiImplOpenGL2Init())
+        //if(!ImGuiImplOpenGL2Init())
+        if(!ImGui_ImplOpenGL3_Init("#version 120"))
         {
             printf("ImGui OpenGL initialization failed!");
             return -3;
         }
     }
-
+    
     ImFontConfig* config = ImFontConfig_ImFontConfig();
     ImGuiIO* io = igGetIO();
     const ushort* font_ranges = ImFontAtlas_GetGlyphRangesDefault(io.Fonts);