Update README.md

Internals: DragBehavior: Added support for ImGuiDragFlags_Vertical to implement a vertical drag widget (no frontend function provided).

Internals: SliderBehavior: Using axis indexing.

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)

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

ListBox(): Fixed frame sizing when items_count==1 unnecessarily showing a scrollbar. (#2173). Tweaked frame sizing so list boxes will look more consistent when FramePadding is far from ItemSpacing.

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

Examples: Add missing include guards (#2166)

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

Internals: Moved the FocusableItemUnregister() outside of InputScalarAsWidgetReplacement(), it should not be here and doesn't facilitate reusing InputScalarAsWidgetReplacement(). (cc #2155)

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

Demo: Removed one level of indentation in the ShowDemoWindowXXX functions (6 kb worth of spaces!). Will break some merge/PR.

Demo: Split the contents of ShowDemoWindow() into smaller functions as it appears to speed up link time with VS. (#2152)

SliderAngle: Added optional `format` argument to allow users customize precision and make localization. (#2150)

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.

Font readme: Added OpenFontIcons, tweaks, links, removed spaces (#2141)

Update README.md

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

Removed unnecessary ImGui:: qualifiers in internal code.

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

Demo: Added comments / tweaks related to the popups.

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)

Fix Clang/GCC's null-conversion warning: (#2081) ...

The warning is "implicit conversion of NULL constant to 'unsigned int' [-Wnull-conversion]". Happens when ImTextureID is not a void*, but unsigned int, for example.