Moved IMGUI_DISABLE_OBSOLETE_FUNCTIONS block lower in the imgui.h file so obsolete functions can use flags. Also sane to quarantine them outside of the respectable area.

Internals: PaintVerts** renamed to ShadeVerts**, moved to imgui_draw.cpp and exposed in imgui_internal.h (+1 squashed commits)

Internals: Added ImLinearSweep() helper.

Internals: RenderCollapseTriangle() -> RenderTriangle(), takes a ImGuiDir

CollapsingHeader(bool*) variant: fixed for IsItemHovered() to work properly in the nav branch.Basically the close button now has to use ItemAdd() to be navable into, which overwrite the IsItemHovered data. (#600, #787)

Internals: ButtonBehavior: made ImGuiButtonFlags_PressedOnClick and ImGuiButtonFlags_PressedOnDoubleClick set the click offset correctly + hold on g.ActiveId so Held state can be reported. Added ImGuiButtonFlags_NoHoldingActiveId flag to disable the later.

Internals:Helpers: Added ImSwap(int,int), exposed ImStrncpy().

Checkbox: Using checkmark. MenuItem: Tweaked checkmark, thicker.

Begin: Work toward obsoleting the 5-arguments Begin() overload. Internal BeginEx() becomes the normal public Begin() again! (4)

Begin: Work toward obsoleting the 5-arguments Begin() overload. Removed bg_alpha from internal BeginEx(). (3)

Begin: Work toward obsoleting the 5-arguments Begin() overload. Removed size_on_first_use from internal BeginEx(). (2)

Begin: Work toward obsoleting the 5-arguments Begin() overload. (1)

Exposed Scrollbar() in imgui_internal.h and removed a bool arg

Internal: ItemAdd(), IsClippedEx(): removed unnecessary indirection for ID parameter

Comments

Merged from Navigation branch: ImGuiItemFlags_SelectableDontClosePopup flag

Added VerticalSeparator() entry point in imgui_internal. Seperator() in an horizontal layout context still does that.

Fixed IsItemHovered() - part of the processing has to be done in ItemAdd() because the widget may alter clipping rectangle temporarily.

Refactor to move the responsability of SetHovered() to ItemHoverable() - previously IsHovered(). Simpler and the parallel to ItemAdd is clearer with the new name.

Internals: ButtonBehavior(), IsHovered() moved the responsability of flatten_child higher level to ButtonBehavior() - not super sure about the elegance of this

IsItemHovered(), ItemAdd(): finishing cleaning up, moved the code to IsItemHovered() so ItemAdd() is more lightweight and the two IsXXXHovered functions are now very similar, making their differences less confusing.

ItemAdd(), not performing computation for IsItemRectHovered() which does them itself, allowing us in the next commit to optimize ItemAdd() and make its logic more consistent with IsHovered().

Removed extraneous ImGui:: prefixes. Declared ColorEditOptionsPopup in imgui_internals.h. Tweaked internal signatures.

ImFontAtlas: Refactored internals API to 1) avoid building lookup table multiple times for merged fonts + 2) allow the mapping of custom icons inside fonts (wip, uncommited)

Separator(): output vertical separator when used in horizontal layout mode, so it works in menu bars.

Exposed PushMultiItemsWidths() to imgui_internal.h

BeginCombo(): rework internals a little to make it easier to provide custom combo-like elements relying in BeginCombo(). ...

BeginPopupEx() doesn't enforce AlwaysAutoResize flag anymore.

SetNextWindowPos: added a ImVec2 pivot parameter for positioning a given a center, bottom-right position, etc. As a generalization of SetNextWindowPosCenter() which is now obsolete. This will be useful for combo-like popups as well. ...

Demo: Simple-overlay window uses the SetWindowPos pivot to select a corner to position itself at.

Popups: Exposing a little more of popups internals in imgui_internals.h

Remove commas after last item in enumeration. ...

This brings these enums to match the rest of the code and fixes
2 warnings under clang about using C++11 extensions.