Merge branch 'master' into viewport ...

# Conflicts:
#	examples/allegro5_example/main.cpp
#	examples/directx10_example/main.cpp
#	examples/directx11_example/main.cpp
#	examples/directx12_example/main.cpp
#	examples/directx9_example/main.cpp
#	examples/imgui_impl_dx10.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_dx9.cpp
#	examples/imgui_impl_glfw.h
#	examples/imgui_impl_vulkan.cpp
#	examples/opengl2_example/imgui_impl_glfw_gl2.cpp
#	examples/opengl2_example/main.cpp
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/opengl3_example/main.cpp
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl2_example/main.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
#	examples/sdl_opengl3_example/main.cpp
#	examples/vulkan_example/main.cpp
#	imgui.cpp
#	imgui.h

Renamed ImGuiStyleVar_Count_ to ImGuiStyleVar_COUNT for consistency with other enums. Added

Added ArrowButton(). Exposed ImGuiDir.

BeginCombo(): Added ImGuiComboFlags_NoArrowButton and ImGuiComboFlags_NoPreview flags + hover color matches drag and sliders.

Viewport: Replaced UpdatePlatformWindows/RenderPlatformWindows by RenderAdditionalViewports(). The update is always called in EndFrame(). (#1542)

Allow user to override ImTextureId. (#1641)

Nav: Added links to PNG/PSD files for PS4 and Switch. Fixed suggested Joy-con mapping as per typical Nintendo-style mapping. (#787)

Added ImGuiConfigFlags_IsSRGB, ImGuiConfigFlags_IsTouchScreen (strictly for user storage)

Renamed ImGuiNavFlags io.NavFlags to ImGuiConfigFlags io.ConfigFlags. (#787)

Renamed ImGuiNavFlags io.NavFlags to ImGuiConfigFlags io.ConfigFlags. (#787)

Viewport: Initial viewport branch+ platform api commit (squashed from previous commits, still very WIP) (#1542)

Removed DisplayVisibleMin/DisplayVisibleMax facility (as part of # 1542). Misc comments.

Merge branch 'master' into examples_refactor ...

# Conflicts:
#	examples/opengl3_example/imgui_impl_glfw_gl3.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp

TreeNode: Renamed Beta ImGuiTreeNodeFlags_NavCloseFromChild to ImGuiTreeNodeFlags_NavLeftJumpsBackHere. (#1079)

Merge branch 'master' into examples_refactor

ImDrawList: PushTextureID(): Removed unnecessary param by reference.

Merge branch 'master' into examples_refactor

Drag and Drop: BeginDragDropSource(): temporarily removed the optional mouse_button=0 parameter because it is really usable in typical conditions at the moment. (#143, #1637)

Added dummy io.DisplayPos field.

ImFontAtlas: Added IsBuilt() helper.

Merged a bunch of small inconsequential things from my work branch, to reduce the diff noise.

Renamed misleading ImGuiMouseCursor_Move to ImGuiMouseCursor_ResizeAll. SDL: Fixed cursor. (#1626)

Obsoleted the io.RenderDrawListsFn callback, you can call your graphics engine render function after ImGui::Render(). Use ImGui::GetDrawData() to retrieve the ImDrawData* to display..(#1599) ...

Examples: Updated examples.

Comments, moved ImFontAtlas::Flags to "public" area.

ImFontAtlas: Added ImFontAtlasFlags_NoPowerOfTwoHeight, ImFontAtlasFlags_NoMouseCursors flags. (#1613)

Fixed legacy forward function IsRootWindowOrAnyChildHovered() broken by a63fbbc

Added IsAnyMouseDown() helper. ...

Examples: DirectX9/10/11: Using IsAnyMouseDown() instead of local function.

Styles: Comments and re-ordered.

Comments

Updated version to 1.60 WIP to emphasis on the addition of required calls CreateContext/DestroyContext + merged the massive Navigation branch (#1565, #787)