Workaround for print failure on non-UTF8 chars

[hrobeers]

Replace non-printable ASCII chars as love.graphics.print refuses to print non-UTF8 chars.

PICO-8 seems to have invented some non-UTF8 chars for icons.

This is a requirement to make fuz work:

To make most carts work, more changes are required, see my other PRs.
Or my workarounds branch: https://github.com/hrobeers/picolove/tree/workarounds

[Shoozza]

Thanks for the workaround, I'll try to add it with a few changes.

• PICO-8 renders unknown chars as an empty space " ".
• If there is an UTF8 char which uses multiple characters it will print space for each char (seems like there is no real UTF8 support).
• Some chars cannot be used in PIC0-8 print, as it will generate an error (0x1a, 0x0d, 0x0a), they probably should do that in picolove as well

In the future a proper implementation should match that of PICO-8