NewFrame: Allow MovedWindow setting the ImGuiWindowFlags_NoInputs after moving has started in order to be able to detect windows below it, which is useful for e.g. docking mechanisms.

NewFrame: Removed unnecessary call to FindHoveredWindow() and simplified code (went through this multiple times, hopefully haven't broken anything)

Merged a bit of code from Navigation branch to ease further merging (InnerRect is currently not required in the Master branch)

Examples: Extra clarification for the 100th person who insist on using the OpenGL2 code in spite of existing documentation leaning against it. (#1394)

Comments about mouse setup and clearing HoveredWindow when mouse down isn't owned by imgui (will affect some future hovered test and drag'n drop patterns) (#143, #1382, #1392)

Added most basic form of Disabled flag to disable interactions (but visuals aren't altered), in imgui_internals.h, undocumented/unsupported (#211, #1012)

(NB: imgui_demo stills uses it)

ImFormatString, ImFormatStringV(): clarifying specs so that passing a NULL buffer should return the desired length. (#1038)

Renamed IMGUI_DISABLE_WIN32_DEFAULT_CLIPBOARD_FUNCS/IMGUI_DISABLE_WIN32_DEFAULT_IME_FUNCS to IMGUI_DISABLE_WIN32_DEFAULT_CLIPBOARD_FUNCTIONS/IMGUI_DISABLE_WIN32_DEFAULT_IME_FUNCTIONS for consistency. (ref #238, #520, #738)

ps: DirectX 12 example (#302) may want to adopt that as well.

ColorButton: Fixed rendering color button with a checkerboard if the transparency comes from the global style.Alpha and not from the actual source color.

Factorized some code (+ declared as static function without namespace, a pattern with the Nav branch has started to use)

Examples: DirectX9/10/11: Renamed WndProc handler to use a generic Win32 name + returning 0 to all messages is more correct.

ps: DirectX 12 example (#302) may want to adopt that as well.

MenuItem(): Tweaks to mimic exact spacing of BeginMenu() when inside a menu bar, which is a little misleading imho but may be useful. (#1387)

Font: Renamed ImFont::Clear() to ImFont::ClearOutputData() for consistency with what ImFontAtlas does. DisplayOffset is set by constructor but not reset by ClearOutputData. (#1349)