Merge branch 'master' into viewport + comments ...

# Conflicts:
#	examples/imgui_impl_opengl3.cpp
#	imgui.cpp

Nav: Fixed an assert in certain circumstance (mostly when using popups) when mouse positions stop being valid. (#2168) + adding a else block to make NavCalcPreferredRefPos() more explicit.

Viewport: BeginMainMenuBar(): explicitly set viewport to avoid creating new one when ImGuiConfigFlags_ViewportsNoMerge is set + misc shallow changes.

Made IsWindowFocused() work outside of NewFrame()-EndFrame() and added comments about how ImGuiFocusedFlags_AnyWindow should NOT be used in place of io.WantCaptureMouse. (#2185)

Viewport: Fixed SDL+OpenGL2 example to work with multi-viewports. (#2175)

Merge branch 'master' into viewport

Config: Added IMGUI_DISABLE_WIN32_FUNCTIONS to disable linking with _any_ Win32 function, as a general forward compatible measure.

Doc: Fixed comments referring to LoadFromFileTTF() instead of AddFontFromFileTTF() (#2153)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Fixed OpenGL texture loading example in comment + Discourse link to root of discourse

Misc comments improvements

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

Viewport, Docking: Fixed incorrectly setting the ImGuiViewportFlags_NoInputs flag, affecting split docking node. (#2109)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp
#	imgui.h

Added ImGuiWindowFlags_NoMouseInputs which is basically the old ImGuiWindowFlags_NoInputs (essentially we have renamed ImGuiWindowFlags_NoInputs to ImGuiWindowFlags_NoMouseInputs). Made the new ImGuiWindowFlags_NoInputs encompass both NoMouseInputs+NoNav, which is consistent with its description. (#1660, #787)

Window: Added ImGuiWindowFlags_NoBackground flag for consistency and to ease creating new flag combinations. Added ImGuiWindowFlags_NoDecoration helper flag which is essentially NoTitleBar+NoResize+NoScrollbar+NoCollapse. (#1660)

Viewport: Exposed GetOverlayDrawList(ImGuiViewport* viewport) in public API. (#1542, #1660, #1878, etc.)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_sdl.cpp
#	imgui.cpp

Revert using wchar_t functions (9cf94d5 + 2eaf5b0). Big mistake, wchar_t is not guaranteed to be 16-bits.

Tests: Added imgui-test engine hooks (experimental).

RenderText(), InputTextMultiline(): Optimization for large text by using memchr, wmemchr, wcschr when appropriate.

Renamed misc/stl/imgui_stl.h,.cpp to misc/cpp/imgui_stdlib.h in prevision for other files.(#2035, #2096) ...

Added misc/README file.

Shutdown: Unlock font atlas before destroying context, so we can destroy a context between NewFrame and EndFrame if we wait (facilitate main loop structures). Internals: GetWindowScrollMaxX(), GetWindowScrollMaxY()

Internal: Moved stored window name update code to the first_begin_of_the_frame block. This will be useful in the Docking branch.

TextUnformatted: Using memchr(), fixed not properly testing for text_end bound + comments. ...

Internals: Added ImStreolRange() + used in LogRenderedText() + comments.

ImGuiTextBuffer: Avoid heap allocation when empty.

Comments + internal using Tab Stop terminology (ImGuiItemFlags_NoTabStop instead of !ImGuiItemFlags_AllowKeyboardFocus)

Viewport: Added ImGuiConfigFlags_ViewportsDecoration to re-enable platform decoration (#1542)

Merge branch 'master' into viewport ...

# Conflicts:
#	imgui.cpp

Window, Inputs: Fixed resizing from edges when io.MousePos is not pixel-rounded by rounding mouse position input. (#2110)