Merge branch 'drag_and_drop'

Drag and Drop: Fix merge for IMGUI_DISABLE_OBSOLETE_FUNCTIONS

Tweak

Begin: Tidying up code to make it more readable.

Fixed ParentWindow setup which broke Modal windows (fix c65124f)

Drag and Drop: Drop target infer a fallback ID from the rectangle. Avoid Preview being accepted on drop frame when drop target has no ID. (#143)

Drag and Drop: Added ImGuiCol_DragDropTarget (#143, #707)

Drag and Drop: Comments

Merge branch 'master' into drag_and_drop ...

# Conflicts:
#	imgui.cpp
#	imgui.h
#	imgui_internal.h

Renamed GetItemsLineHeightWithSpacing() to GetFrameHeightWithSpacing()

Added GetFrameHeight() function (used to be SmallSquareSize internally)

Internals: Added GetSmallSquareSize()

IsWindowFocused() refactor will flags. (#1382) ...

Marked IsRootWindowFocused() as obsolete in favor of using IsWindowFocused(ImGuiFocusedFlags_RootWindow).
Marked IsRootWindowOrAnyChildFocused() as obsolete in favor of using IsWindowFocused(ImGuiFocusedFlags_RootAndChildWindows).

Internals: ParentWindow is now NULL for non-child windows and means what everyone expects.

Internals: Removed misleading GetWindowParent() function. + renaming to clear confusing.

IsWindowHovered(): split ImGuiHoveredFlags_FlattenChild into separate ChildWindows and RootWindow flags. Allowing more combination and a better symetry with IsWindowFocused() flags. (#1382)

Renamed ImGuiTreeNodeFlags_AllowOverlapMode to ImGuiTreeNodeFlags_AllowItemOverlap. (#600, #1330)

Internals: Renamed ImGuiButtonFlags_FlattenChilds -> ImGuiButtonFlags_FlattenChildren, ImGuiButtonFlags_AllowOverlapMode -> ImGuiButtonFlags_AllowItemOverlap

Merge branch 'master' into drag_and_drop ...

# Conflicts:
#	imgui.cpp
#	imgui.h

Added an implementation of SetItemDefaultFocus() in the master branch for combo patterns to use and be more forward-compatible. (#787)

Exposed BeginCombo() publicly.

SetNextWindowContentSize() adjust for client->window size, but the fate of borders isn't really clear for now (until now we always tried to make borders not affect layout, so if we want a 200x200 fully visible space with borders and zero window padding user need to include the borders) (#1490)

Scrollbar: Minor simplication of the code using InnerRect data.

Internals: window->InnerRect includes removal of borders so it'll be easier to use from other locations.

Fix for border under title bar when WindowBorderSize == 0 and FrameBorderSize > 0

Removed SetNextWindowContentWidth(), prefer using SetNextWindowContentSize(). Kept redirection function (will obsolete). (#246, #519, #1444)

Fixed warning: logical ‘and’ of equal expressions

ColorPicker4: Fixed returning true when holding mouse button on the sat/value/alpha locations. (#1489)

ColorEdit4: Made IsItemActive() return true when picker popup is active. (#1489)

Combo: Removed ImGuiWindowFlags_ComboBox flag. Moved internal window flags.