Since the URHO3D_PCH build option is made available to support non-PCH build, our build system does not rely on precompiled header to include the Urho3D.h export header anymore. The export header is auto-included by one of Urho3D headers when it is required using the right format with the help of URHO3D_IS_BUILDING compiler define. As such, there is no need to explicitly include Urho3D.h in external project too. Sorry for the flip-flop.
It is now a library user own's responsibility to include the Urho3D.h in their source code. Or to include it as part of their own precompiled header similar to what Urho3D project has done.
Added diffuse unlit & notexture unlit techniques.
Do not use occlusion if viewport is very tall compared to width, as the pixel width of the occlusion buffer is fixed and would result in large CPU time consumption.
