add support for TI-84+ CE

[AreaOfZero]

This project looks great, but I unfortunately can't use this forth implementation because the binary can't run on the TI-84+ CE because of the switch over to the eZ80 microprocessor. I would attempt to write an eZ80 version of the assembly code and submit a PR myself, but I'm not familiar with Z80/eZ80 assembly at all. The new include file for the TI-84+ CE would likely be very helpful in adding support for it: ti84pce.

If I get some more time, I may try to learn eZ80 asm myself so I can help out.

[siraben]

Thanks for checking out the project! Yeah, this project will only run on TI-84+ or TI-83 (at least one other user has reported it working there). I'm not familiar enough with eZ80 nor do I use TI calculators any more. If you manage to get it working, let me know. You can reduce the number of words and focus on the core functionality, and port the syscalls to work with display and keyboard interaction.