Add ability to test arbitrary rectangle for visibility without need of moving cursor.

Using ImGuiID instead of ImU32 is a few places

SameLine() with explicit X position is relative to left of group/columns (ref #746, #125, #630)

InputTextEx: got rid of unnecessary locals.

InputTextEx(): more shallow tidying up, still being cautious with this function

InputText/IO: Got rid of individual OSX options in ImGuiIO, added io.OSXBehaviors (#473, #650)

InputTextEx(): minor tidying up

InputText(): minor tidying up/simplification following changes for osx style improvements (#650)

Merge branch 'add-osx-homeend-keys' of https://github.com/michaelbartnett/imgui into michaelbartnett-add-osx-homeend-keys

Begin: Moved code that calls FocusWindow() on a newly appearing window lower in the function so that Nav branch can use CursorStartPos on the first window frame. (#323) ...

Pushing in master because it _should_ be a no-op but I'd rather test for any issue in Begin() as soon as possible.

Closing the focused window restore focus to the first active root window in descending z-order (part of #727)

Fixed scrolling offset when using SetScrollY(), SetScrollFromPosY(), SetScrollHere() with menu bar. ...

Tests:
a) add SetScrollY(+20) after Begin("ImGui Demo") test with/without title/menu.
b) add ImGuiWindowFlags_MenuBar in BeginChild() in scrolling tracking demo.

Windows: No default IME handler when compiling using GCC. (#738)

TODO list

InputTextMultiline(): fix so that IsItemActive() can be used afterwards (otherwise the info was lost by using child/group)

InputTextEx: comments (related to #725)

InputTextMultiline(): partial fix for when input and internal buffers differs in a way where scrollbar existence differs. (#725) ...

Partial fix, won't stop ids from functioning because of a zombie id.

add shortcut+backspace support

osx uses super+arrows for home/end, built on work in ocornut/imgui#473

Using GetCurrentWindowRead() instead of GetCurrentWindow()

SetCursorScreenPos() fixed not adjusting CursorMaxPos as well

ImGuiListClipper: Fix to behave within column (#661, #662, #716)

ImGuiListClipper: fixed automatic-height calc path dumbly having user display element 0 twice (#661, #716) ...

First bug out of two. Was easily visible using e.g. 50% alpha text.

NextColumn() tidying up with a sane early out

Added assert to track stb_textedit.h issue (#715)

InputTextMultiline(): Fixed Ctrl+DownArrow moving scrolling out of bounds

Fixed Windows default clipboard leaving its buffer unfreed on application's exit. (#714)

Minor bits

Comments amend 3c8e490 (committed before saving last comment edit) (#703)

Comment on dealing with io.WantCaptureKeyboard (#703)