Fix button label position

This reverts a portion of hrev46580 concerning placement of a label on a button.
The label was draw too low on the button in some cases, notably in Keymap.
Restoring the old code for the icon-less case fixes the problem.

There still may be a problem drawing labels on buttons with icons, but, the code
should behave the same as it did in hrev46580 for that case, which is when
buttons with icons was introduced.