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.

Update README.md

Fixed typo in misc/README.txt (#2131)

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).

Fixes crash introduced in previous commit 9cf94d5.

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.

InputText: Clarified comments around ImGuiInputTextFlags_CallbackResize and other callbacks. (#2006, #1443, #1008)

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()

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)

Update README.md

Update README.md

Examples: OpenGL3: Cast compile/link status to GLboolean (#2112, #2125) ...

Some OpenGL loaders/bindings do not allow comparisons between GLints and GLbooleans.

Examples: imgui_imp_opengl3.cpp explicit casting for overly aggressive glbinding compatibility. (#2112) [@hesiod]

Examples: DirectX10, DirectX11: Removed seemingly unnecessary calls to invalidate and recreate device objects in the WM_SIZE handler. (#2088)

Fix spacing in imgui_imp_sdl example (#2111)

Update pull_request_template.md