* Now decides whether the menu is above or below the target position
before rendering it. This causes its position to no longer vary
depending on the length of completions
* When the text area is height constrained (< 12) lines, now chooses the
side which has the most space. Before it would always display above if
height constrained below.
* Misc code cleanups
Release Notes:
- Improved completions menu layout to be more stable and use available
space better.
a062c0f1bc