Added GetItemRectSize(). Renamed GetItemRectMin()/GetItemRectMax()/IsMouseHoveringBox() to GetItemRectMin()/GetItemRectMax()/IsMouseHovering

Maintaining DC.CursorMaxPos instead of SizeContentsCurrent, simpler, faster and easier to understand.

Various fixes related to vertical alignment of text after widget of various sizes. Added demos. Toward #160

Also fixed LabelText() height.

Examples: OpenGL: if content window doesn't have focus, tell ImGui we don't have a mouse position.

opengl3+opengl example: if content window doesn't have focus, tell ImGui we don't have a mouse position.  e.g. avoids tooltips popping up in imgui app when you're interacting with a different app window that overlaps it.

Examples: DirectX9: fixed duplicate creation of vertex buffer. Size of static vertex buffer at top of the code.

No recursion in any of those functions. Tho keeping a lock api may be
preferable?

Renamed style.TreeNodeSpacing to style.IndentSpacing, ImGuiStyleVar_TreeNodeSpacing to ImGuiStyleVar_IndentSpacing

+ right align all widgets

Not really happy about them