Build fix for master.

Examples: SDL: Avoid testing for SDL_GetKeyboardFocus() on Android and iOS (like Emscripten). (#421)

Examples: Setting up style before bindings, so in complex binding (vulkan/dx12) it isn't miles away from the context creation.

Examples: DirectX10/11/12: Made imgui_impl_dx10/dx11/dx12.cpp link d3dcompiler.lib from the .cpp file to ease integration.

Version 1.66b (will revisit how to change IMGUI_VERSION_NUM across versions, this commit reduces the numerical IMGUI_VERSION_NUM compared to the commit on Nov 22).

Fixed typo.

About, IO: Added io.BackendPlatformName, io.BackendRendererName for informational/QA purpose.

Examples: SDL: changed the signature of ImGui_ImplSDL2_ProcessEvent() to use a const SDL_Event*. (#2187)

Examples: SDL2+Vulkan: Fixed application shutdown which could deadlock on Linux + Xorg. (#2181)

Examples: OpenGL3: More explicit testing for == GL_UPPER_LEFT in case glGetIntegerv(GL_CLIP_ORIGIN is not honored properly. (#2186, #2195) Fix f52f0a5

Examples: OpenGL3: Added support for GL 4.5's glClipControl(GL_UPPER_LEFT). (#2186)

Examples: GLFW: User previously installed GLFW callbacks are now saved and chain-called by the default callbacks. (#1759)

Examples: Misc comments mainly related to GLFW callbacks. (#1759)

Examples: OpenGL3+GLFW/SDL: Made main.cpp compile with IMGUI_IMPL_OPENGL_LOADER_CUSTOM (may be missing init). (#2178)

Examples: SDL: Tweaked Windows instructions and batch files. (#2175)

Examples: GLFW: VS2015 project link with legacy_stdio_definitions.lib in order to link with the precompiled VS2010 GLFW3.lib we provide. (#2010, #2043, #2091)

Examples: Add missing include guards (#2166)

Examples: Vulkan: Avoid unreferenced parameter warning. (#2162)

gladLoadGL() return 0 to indicate failure (#2157)

Comments in demo and opengl code + Internals: Added HoveredIdNotActiveTimer tracking hovering time unless the item is active, which is a commonly useful pattern.

Examples: Downgraded Xcode project object version (50->48) to support Xcode 9.2 (last version supported on macOS 10.12) (#2133, #1929)

Examples: Downgraded Xcode project object version (50->48) to support Xcode 9.2 (last version supported on macOS 10.12) (#2133)

Examples: OpenGL3: Cast compile/link status to GLboolean (#2112, #2125) ...

Some OpenGL loaders/bindings do not allow comparisons between GLints and GLbooleans.

Examples: imgui_imp_opengl3.cpp explicit casting for overly aggressive glbinding compatibility. (#2112) [@hesiod]

Examples: DirectX10, DirectX11: Removed seemingly unnecessary calls to invalidate and recreate device objects in the WM_SIZE handler. (#2088)

Fix spacing in imgui_imp_sdl example (#2111)

Examples: Vulkan: Fixed some minor discrepency in the SDL+Vulkan example to match the Glfw+Vulkan example. (cc #2097)

Examples: Referring to missing gamepad support in back-end that are missing it.

Examples: Using "dear imgui" terminology in all examples headers/comments + fix minor typo.

Internals: Replace unsigned short with ImWchar when dealing with character storage (missing cases) + in imgui_impl_ file keep using neutral type everywhere, added missing explicit cast in three bindings. (#2078)