Nav: SetActiveId() uses SetActiveIDNoNav() to avoid duplicating logic. (#787)

Nav: Extract part of NavUpdate() into a saner NavScrollToBringItemIntoView() (#787)

Nav: More consistently drawing a (thin) navigation rectangle hover filled frames such as tree nodes, collapsing header, menus. (#787)

Merge branch 'master' into navigation

Rnamed AlignFirstTextHeightToWidgets() to AlignTextToFramePadding(). Kept inline redirection function (will obsolete).

TreeNode: Added ImGuiTreeNodeFlags_FramePadding flag

Nav: Renaming NavInitDefaultRequest -> NavInitRequest

Nav: Moving code next to its peers

Nav: Caching into g.NavAnyRequest to minimize hot path cost (and so we can add many more request sources)

Nav: Minor tweaks in NavProcessItem() used by ItemAdd()

Nav: Minor tweaks also toward removing processing from ItemAdd()

Internal: ItemAdd() minor shallow tweaks

Merge branch 'master' into navigation ...

# Conflicts:
#	imgui.cpp
#	imgui_internal.h

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

Removed extraneous calls to GetCurrentWindowRead() when we already have a ImGuiContext. Internal RenderXXX functions also don't need to write into the Accessed field at all.

Merge branch 'master' into navigation

Nav: Shuffled code in ItemAdd() so that NavProcessItem() may have access to LastItemId (will be required by tabbing)

Nav: Minor midying up and comments,

Nav: Removed possibly redundant test prior to calling NavProcessItem() from ItemAdd()

Nav: Moving code next to its peers

Nav: Moving the big chunk of code from ItemAdd() to NavProcessItem()

Added ActivateItem(), GetItemID() functions.

Nav: Tidying up activation mechanism so that setting NavActivateId can trigger buttons.

ColorButton: Reduced bordering artefact that would be particularly visible with opaque Col_FrameBg and FrameRounding enabled.

TextUnformatted(): minor tweak

Made AlignFirstTextHeightToWidgets() saner and faster (still disliking its name very much!)

Merge branch 'master' into navigation

Nav: Menus and popups now have move request wrap around vertically (using the move request forward thing added recently). (#787)

SetKeyboardFocusHere() added assert to prevent passing values smaller than -1 as we may have to outlaw them (I think nobody was using that)

Removed obsolete comment.