TEENSY: Add flash and SD card file system

[Joe7M]

Hi Chris,

• I added a persistent flash file system for the Teensy. Users can access the memory to store data. If a MAIN.BAS is found in flash memory, it will be executed at every start of the Teensy. Once flash worked I realized that adding the sd card is quite simple.
• Because the file teensy.cpp got too large, I split it in several small files.
• I added new examples and new hardware (LCD text display and a I2C accelerometer).
• I added a handler which get executed when a module is closed. I needed it to close open files, otherwise it happened quite often, that the files were empty after restart.
• You can upload the file console.bas to the Teensy to get a simple console where you can use commands like ls or cp to manage your files on the Teensy. Type "help" for a list of commands.

Best regards, Joerg

[chrisws]

This looks fantasic. I'm looking forward to giving it a try on my board.
Could you please:

1. add an entry to the ChangeLog file following the same format
2. add the following header to each of the source files (or something close to this)

// This file is part of SmallBASIC
//
// Copyright(C) 2026 Joerg Siebenmorgen
//
// This program is distributed under the terms of the GPL v2.0 or later
// Download the GNU Public License (GPL) from www.gnu.org
//

[Joe7M]

I did the changes. I also added a bug fix when building for Windows using MSYS2. Compiling stopped with this __p__environ-warning.

Try it on your Teensy and let me know if you find bugs.