Add debug rendering, fix misaligned pos render bug

Rendering using a non-default quad specifies normalised coordinates
relative to the frame buffer size. Hence each render of these frames
should origin from (0,0) any other value is invalid.

Dengine.vcxproj

@@ -121,6 +121,7 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <ClCompile Include="src\AssetManager.c" />
+    <ClCompile Include="src\Common.c" />
     <ClCompile Include="src\dengine.c" />
     <ClCompile Include="src\Platform.c" />
     <ClCompile Include="src\Renderer.c" />