issue_219_fix - Additional status bar height

When the status bar height is doubled (40 instead of 20), the
calculated location of the inputToolbar is 20 points lower than it
should be. I don’t like hardcoding the default status bar height
(20.0f), but couldn’t find a way to get it.

I tested the follow two cases:
- Status bar height changes due to incoming phone call (in simulator Hardware --> Toggle In-Call Status Bar).
- Status bar height is larger before loading/viewing the MessagesChatView, when the "Personal Hotspot" is already status bar is showing.