Examples: Visual Studio: Updated default platform toolset+sdk in vcproj files from v100+sdk7 (vs2010) to v110+sdk8 (vs2012). This is mostly so we can remove reliance on DXSDK_DIR for the DX10/DX11 example, which if existing and when switching to recent SDK ends up conflicting and creating warnings.

Refactor: Added empty imgui_widgets.cpp + updated project files / makefiles etc. accordingly (#2036)

Examples: Allegro5: Added support for ImGuiConfigFlags_NoMouseCursorChange flag. Added clipboard support. Unindexing buffers ourselves as Allegro indexed drawing primitives are buggy in the DirectX9 back-end.