Tables: added ImGuiTableFlags_NoHostExtendX instead of using outer_size.x == 0.0f. Changed default outer_size to (0.0f, 0.0f). (#3605)

BeginChild: half-fixed child window name longer than 255 conflicting, merely raised the limit by using our shared large buffer. Comments.

Added experimental io.ConfigDragClickToInputText feature to enable turning DragXXX widgets into text input with a simple mouse click-release (without moving). (#3737)

+ Offset ImGuiTableColumnFlags values.

DragFloat, DragInt: very slightly increased mouse drag threshold + expressing it as a factor of default value + disabled experimental click-to-input on DragXXX functions. (#3737)

Tables: rework submission of content size and ideal content size to outer window (now using IdealMaxPos introduced in 6af92b05).

See Tests suite "table_reported_size_outer".

ImBitArray: Rename ClearBits() to ClearAllBits() and add SetAllBits(). ImBitArraySetBitRange work on range [n..n2) instead of [n..n2]

Tables: Clear scroll value when reactivating scroll. Assert when passing width/weight to TableSetupColumn() without an explicit sizing policy at either table or column label.

Clearing scroll was initially made desirable by tests exhibiting side effects but generally feels saner.
table->UserOuterSize is poorly used in this commit but will be by subsequent commits.

Tab Bar: Requested ideal content size (for auto-fit) doesn't affect horizontal scrolling. Followup to afa01d8. (#3414)

+ minor Table rename

Internals: Layout: maintain two content sizes, optionally writing to IdealMaxPos to distinguish used from ideal size, later is used for auto-fit. Unused in this commit, should be no-op. (#3414)

# Conflicts:
#	imgui.cpp

Makes not much difference for inner-scrolling but makes a difference when reported to outer-window.

Tables: Fixed very small tables edge cases: inverted clip rect with freezing + scroll, missing borders.

Demo tweaks. Moved Tabs to Widgets section. Added to Tables demo. Increased version following 00b35c08.

Tables: (breaking) removed ImGuiTableColumnFlags_WidthAuto which now can be expressed as _Fixed + _NoResize. WidthRequest gets updated when RequestOutputMaskByIndex is set rather than Visible.

Tables: fixed border straying out of rect when using ImGuiTableFlags_NoBordersInBody with small height.

Tables: fixed outer_width misreported to layout for use with SameLine when ScrollY is set but not ScrollX (#3704, #3414)

- Attempt to load d3d12.dll from local D3D12On7 paths before falling back to System32
- Do not statically import D3D12SerializeRootSignature

Backends: DX12: Fix warning (#3706). Disable obsolete Tables enums, leave them commented out. Using _MSVC_LANG to enable offsetof() and static_assert() on VS2015.3+

Tables: (Breaking) Added ImGuiTableFlags_SizingFixedSame, ImGuiTableFlags_SizingStretchProp. Removed ImGuiTableFlags_SameWidths.

Simplified some code and clariffied that currently non-resizable = always revert to default (while waiting to untangle Fixed vs Auto and programmatic override not going through TableSetupColumn)
Whereas ImGuiTableFlags_SameWidths has some unusual handling of mixed Fixed/Stretch columns, we know treat them separately.

Tables: Tidying up. Shuffle some columns fields to facilitate debugging + comments + demo tweaks + metrics highlight.

Tables: (Breaking) rename ImGuiTableFlags_SizingPolicyFixed > ImGuiTableFlags_SizingFixedFit, ImGuiTableFlags_SizingPolicyStretch > ImGuiTableFlags_SizingStretchSame in prevision for new policies.

Tables: Moved demo chunks. Made right-most non-resizable same-width column hidden to alleviate the issue where they are off by 1 pixel.

ImDrawList: Internals: Add ability to scale anti-alias fringe. This enable users to keep geometry sharp while scaling vertex buffer content.

Fixed using IsItemEdited() after Combo() not matching the return value from Combo(). (#2034) + fix some PVS warnings, fix typo, blanks.

Amend e28b1078

Backends: OpenGL2, OpenGL3: Backup and restore GL_SHADE_MODAL, GL_STENCIL_TEST, clear GL_NORMAL_ARRAY. Comments., (#3671, #3668)

Tables: Fix hiding column right after the frozen line. Fix hovering/resising column delimiter scrolled under frozen columns. (#3678)

Added 64-bit variants of CheckboxFlags() in imgui_internal.h. Improve assert on mismatched ListBoxFooter() call. Fix FAQ index. (#3687)

Inputs: Internal: added SetItemUsingMouseWheel() and mechanism to request mouse wheel for both HoveredId and ActiveId. (#2891)

Based on @kudaba PR.

Tables: internal tidying up, calculate WidthAuto in first loop of layout + TableSetupColumn() with unspecified stretch weight leaves it at -1.0f (unset) rather than overrding default. Amend 3b3503e6.

Both changes are intended to have no side-effects. Committed separately from upcoming commit for easier future bissecting.
Small demo fix.

Tables: report auto-fit width in EndTable(), extracted TableGetColumnWidthAuto(). fix minor flickering with IsPreserveWidthAuto (which is a debug feature still), moved some code.

Tables: (breaking) rename ImGuiTableFlags_ColumnsWidthStretch > ImGuiTableFlags_SizingPolicyStretch, ImGuiTableFlags_ColumnsWidthFixed > ImGuiTableFlags_SizingPolicyFixed in prevision for other policies.