Merge branch 'master' into docking

Vulkan: Avoid passing negative coordinates to vkCmdSetScissor, which debug validation layers do not like.

Viewport: Fixed PushClipRectFullScreen() missing out on negative coordinates. Among other things, the outer highlight during CTRL+Tab wouldn't appear in negative coordinates monitors. (~#2176, #1542)

Tabs to Spaces, comments.

Renamed freeglut vcxproj files + Comments, Changelog (#2465)

freeglut -> glut rename

ifdef freeglut extensions properly

Fixups for OSX

Add makefile for freeglut

Examples: Vulkan: Added shader sources/references in the .cpp source.

Merge branch 'master' into docking ...

# Conflicts:
#	examples/imgui_impl_dx9.cpp
#	examples/imgui_impl_opengl3.cpp

InputText: Made Shift+Tab consistently do nothing regardless of whether the back-end emits both char and keys or just keys. (#2467, #1336)

InputText, Examples/SDL: Emulate \t input if back-end doesn't provide it. (#1336, #2467) ...

+ Fix some output filename in SDL build batch files.

InputText: Fixed ImGuiInputTextFlags_AllowTabInput leading to two tabs characters being inserted if the back-end provided both Key and Character input. (#2467, #1336)

InputText: Work-around for buggy standard libraries where isprint('\t') returns true. (#2467, #1336) ...

Not using isprint. + todo items.

Examples: Vulkan: Using IM_ARRAYSIZE() where possible.

Examples: Vulkan: Added missing support for 32-bit indices (#define ImDrawIdx unsigned int). + demo typo

Silencing -Wstack-protector (#2459)

Examples: DirectX9: Fixed erroneous assert in ImGui_ImplDX9_InvalidateDeviceObjects(). FreeType: Fixed suggested code to not require an initial build call.. (#2454)

Examples: DirectX12: Various tidying up.

Examples: OpenGL3: Minor tweaks, clarifications + not calling glBindBuffer more than necessary in the render loop.

Docking: Fixed focus restore lagging by a frame when a tab stops being submitted. (#2109) Building on a little build of technical debt there, should transition toward a more general docking-agnostic system (#2304)

Viewport: Renamed member + added note about a Docking issue with restoring focus.

Docking: Remove code in BeginDocked() to set HiddenFramesCannotSkipItems based on upcoming tab bar selection, solely based on focus (might break something subtle?). Follow-up to c355ed1. (#2453, #2109)

Docking: Disable SkipItems when directly/programmatically focused (possible generalization of code currently in BeginDocked which relies on tab bar interaction, will remove that code in next commit). (#2453, #2109)

Merge branch 'master' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt
#	imgui.cpp

Internals: Renamed the ImGuiWindow HiddenFrameXXX fields to decorrelate them from resizing behavior, as those values are set by other logic.

Docking: Added ImGuiDockNodeFlags_NoTabBar (not exposed publicly). (#2423, #2109)

Docking: Internals: Moved CentralNode and HiddenTabBar state into LocalFlags for consistency. (#2423, #2109)

Docking: Separating SharedFlags vs LocalFlags in dock node so settings can be applied to individual nodes. Made _NoResize logic on single node applies as expected. (#2423, #2109)