Docking: Comments and renaming locals to facilitate debugging.

Merge branch 'viewport' into docking ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/README.txt
#	imgui.cpp

Fixed range-version of PushID() and GetID() not honoring the ### operator to restart from the seed value.

Internals: Tweaks. Comments about PushID/GetID public function.

ImHash: Moved crc32 table out of the function so it can be shared, also avoid cases were compiler tries to makes its initialization thread-safe.

avoid floating point exception when _EM_OVERFLOW is enabled (#2303)

Comments

Fixed using imgui_freetype.cpp in unity builds. (#2302)

Removed trailing spaces from text files. (#2038, #2299)

ImGuiTextBuffer: Added append() function (unformatted).

Merge branch 'viewport' into docking ...

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

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/example_sdl_vulkan/main.cpp
#	examples/imgui_impl_dx11.cpp
#	examples/imgui_impl_dx12.cpp
#	examples/imgui_impl_glfw.cpp
#	examples/imgui_impl_sdl.cpp
#	examples/imgui_impl_vulkan.h
#	imgui.cpp

Examples: OpenGL2: Added (yet another) comment/instruction against using opengl2 with modern OpenGL. (#2297)

Removed trailing spaces (#2038, #2299)

Update for stb_ files. (#2038)

Added checks for "zero-as-null-pointer-constant" warnings for older Clang (#2299, followup to #2277)

Fix the year for screenshot gallery part 7 and 8 links (#2298)

Comments about DLL boundaries and using TLS variables for GImGui. (#2292)

Merge branch 'master' into viewport ...

# Conflicts:
#	examples/imgui_impl_win32.cpp

Qt links

Examples: Win32: Using wc.lpszClassName instead of duplicating the literal. + tweak README format.

Examples: Win32: Added support for mouse buttons 4 and 5 via WM_XBUTTON* messages. (#2264)

ImFontAtlas: Added 0x2000-0x206F general punctuation range to default ChineseFull/ChineseSimplifiedCommon ranges. (#2093)

Examples: Win32: Fix for older Windows SDK.

Merge branch 'viewport' into docking ...

# Conflicts:
#	docs/CHANGELOG.txt

Merge branch 'master' into viewport ...

# Conflicts:
#	docs/CHANGELOG.txt
#	examples/imgui_impl_win32.cpp
#	imgui_demo.cpp

Examples: Win32: Using IsChild() to be compatible with windows created within a parent. (#1951, #2087, #2156, #2232)

Examples: DirectX9: Explicitly disable fog (D3DRS_FOGENABLE) before drawing in case user state has it set. (#2288, #2290)

EditorConfig: Further tweaks (#2038)