Internals: Window minor internal renaming + added WindowRounding latch.

Style: renamed style.ChildWindowRounding to style.ChildRounding, ImGuiStyleVar_ChildWindowRounding to ImGuiStyleVar_ChildRounding.

Style: ScaleAllSizes() helper rounds down every values so they are aligned on integers.

Columns: Added ImGuiColumnsFlags_GrowParentContentsSize to internal API to restore old content sizes behavior. (#1444, #125)

Internals: Updating condition/allow flags with a function.

Internals: Window: Store whether the windows has a close button (we need that info for window/tabs dropping preview calculation)

Internals: Added BringWindowToFront(), BringWindowToBack() helpers.

Windows with MenuBar have a larger minimum height to avoid artefacts (I fixed most of the vertical/horizontal artefacts, but the ones in rounded corners were too hard to fix).

Menu: Fixed minor rendering issues on the right size with rounded window when resizing a window small.

Scrollbar: Minor graphical fix for when scrollbar don't have enough visible space to display the full grab.

Minor comments, tweaks

Make it possible to use SetNextWindowPos() on a child window. Useful internally.

Made it guaranteed by API that after calling Begin() the last Item represent the title bar. (#823)

Scrollbar flicker fix for menus/popups (fixes 4d00dd8 and 2df8fa9). Hopefully right this time.

Columns: Clipping columns borders on Y axis on CPU because some GPU drivers appears to be unhappy with triangle spanning large regions (not sure why tbh). (#125) ...

Demo: Columns: Adding a billion of extra lines and using clipper.

Fixed build (3e06450 not meant for master branch, but ok)

Internals: Added ArrowButton() helper.

Fixed scrollbar flickering on/off when uncollapsing a window (fixes 2df8fa9)

io.OptNoCursorBlink -> io.OptCursorBlink (#1427)

Added io.OptNoCursorBlink option to disable cursor blinking. (#1427). Renamed io.OSXBehaviors to io.OptMacOSXBehaviors. Should affect users as the compile-time default is usually enough. (#473, #650)

Clean g.WindowsById storage on shutdown.

Begin: Fixed appending into a child window with a second Begin() from a different window stack querying the wrong window for the window->Collapsed test.

ButtonBehavior: Fixed ImGuiButtonFlags_AllowOverlapMode to avoid temporarily activating widgets on click before they have been correctly double-hovered. (#319, #600)

Fixed vertical scrollbar flickering/appearing, typically when manually resizing and using a pattern of filling available height (e.g. full sized BeginChild). THIS IS A GREAT FIX, this glitch was nasty and annoying (and yet somehow nobody reported it?). Hopefully haven't broken anything else...

Minor tweaks/comments. Note that the reordering the one subtraction caused subtle havoc before the patch in 9ac8820.

Fixed non-pixel aligned bounding box of window resize grip, / which triumphally led to any re-arrangement of operations inside the resize grip code outputting non-exact size_target values which led to unstable window position because clamping code uses size in a subtraction, etc etc. Lovely how a whole system can be made to act weird with a single bad input.

Child window with MenuBar use regular WindowPadding.y so layout look consistent in child or in a regular window.

ButtonBehavior: Fixed ImGuiButtonFlags_NoHoldingActiveID from incorrectly setting ActiveIdClickOffset, which probably have no known effect, but it is more correct this way. (#1418)

LowerBound() minor tweaks

Internal: FindWindowByName() faster and doesn't touch every windows