Columns: Undo accidental change from 807d4ff

Columns:: columns set with no implicit id include the columns count into the id to avoid collisions (#125)

Columns: minor tidying up while investigating severe issues with indenting within columns (#414)

Columns: avoid growing ColumnsData vector when closing a window with no columns (#125) ...

(Will break calling GetColumnOffset() when there's no column but it
would only have worked after the first frame anyway, so basically it
didn't work)

Columns: tidying up, moving OffsetT to a ImGuiColumnData structure

Rename internal ColumnsStartX to IndentX, makes more sense

InputText: Added password mode via ImGuiInputTextFlags_Password (#237, #363, #374)

ImageButton() uses FrameRounding up to a maximum of available framing size (#394)

Minor popups comment tweak (#402)

Moving stdlib.h include outside of imgui.h (#405)

Fixed unused variable warning if asserts are compiled out.

Fixed a couple of problems found by CppCat code analyzer. ...

* incorrect implementation of ImVec4 operator- which always gives a w value of 0
* boolean formula of ((A && B) || B) can be simplified to just (B)

TODO notes

Fixed Shutdown() not clearing FontAtlas if NewFrame() was never called. (#396, #303)

Refactor internal SliderBehavior() to take flags instead of a bool. ...

Sorry!

Refactor - Internal ButtonBehavior() removed unnecessary boolean arg, merged into flags using ImGuiButtonFlags_NoKeyModifiers. ...

This is quite a risky change frankly but I'd rather refactor sooner than
later. Hopefully few people are using the internal functions.

ColorEdit4: Fixed broken tooltip on hovering the color button (actually fixes #373, #380)

Version number 1.47 WIP

Version 1.46

Fix to allow using SetNextWindow* functions with ImGuiSetCond_Appearing on modal windows (#377) ...

Also affect other popups which called FindBestPopupWindowPos() on their
second frame but it most often acts as a no-op but it wouldn't be
noticeable.

Tweaks (calling inner SetNext* functions directly from Begin)

Renamed Window LastFrameDrawn to LastFrameActive, more correct

ColorEdit4: hovering the color button shows correct alpha (fix #373)

ColorConvertFloat4ToU32() round the floats instead of truncating them.

InputText(): always use live input data for display in read-only mode (fix #360)

Scrollbar: background color less translucent in default style (flattened alpha) so it works better on non-WindowBg colored background.

Scrollbar: fixed vertical alignment with border + no menu bar (following #365)

InputText: removed the need for text_end pointer in the cursor position calculation loop, allows switching buffers

InputText: comments.

InputText: added comments and somehow clarified the optimized code that calculate text position + updated demo