Bug-fix release 1.16.3.1

This release:

• fixes return stack usage issues with the PicoCalc screenshot tools, which were causing crashes when run in tasks other than the PicoCalc terminal emulator screenshot task due to return stack exhaustion.
• fixes an issue with the text-only PicoCalc screenshot tool where it would crash when the font was other than 5x8, 6x8, or 7x8.
• adds a new version of the 'Bricks' (a Breakout clone) game that uses the new 'keymap' mechanism.

Note that this release uses the same kernels as release 1.16.3, so the reported version is still 1.16.3.