On-screen keyboard (visible when the feature is enabled, while
using the "Text" and "Label" tools) now appears with larger
(48x48 pixel, vs 24x24 pixel) buttons, when Tux Paint's window
(or fullscreen) size is large enough to fit them with the
chosen layout.
(h/t Anat & Aviv, who suggested it to help with users of
eye-tracking systems)
Also, on-screen keyboard buttons use a slightly larger font
(16pt vs 12pt, previously seen on the small keyboard;
32pt on the large keyboard).
