System
* Rework script synchronization mechanism (Now verifies scripts using CRC's when stop button is pressed. This can be 20x faster than the previous mechanism.)
* Increase the ping timeout to avoid occasional spurious disconnects
* Update Linux versions to use SDL 2.0.12 graphics library
* Tweak Linux versions to handle change in font rendering introduced in Ubuntu 20.04
* Improve speed of tilt blocks by increasing i2c clock speed on boards that use Wire1 (internal i2c bus)
* Optimize acceleration primitive
* Remove IOT-BUS as a built-in, precompiled VM (sadly, OddWires has gone out of business)

Libraries
* Tone library: Tweak wording of "play note" block
* Tone library: Use "ms" instead of "milliseconds" everywhere
* Change range of tilt and acceleration blocks so that 1 gravity is 100 (previously 50)
* Add support for M5StickC and Calliope to Tone library
* Add José García's BMP and WAV libraries

Examples
* Update DAC pins in examples to work on both the ED1 and M5Stack out of the box
* Update music example projects
* Hide helper functions in some examples to speed up loading in browser version of MicroBlocks
* Add HappyBirthday example
* Add RadioTexting example

Bug Fixes
* Fix: Adding/deleting variables or libraries could result in script errors until "stop" button pressed
* Fix: Make stopTone() also stop buffered sound output so stop button will turn off all sound output
* Fix: i2c could hang when using Tone or Servos on micro:bit (e.g. using the tilt or acceleration blocks)
* Fix: update project blockSpecs when auto-updating a library
* Fix: fetchLatestVersionNumber missed the major version number (wasn't causing trouble yet because nil ~= 0)
* Fix: Pasting empty scripts from clipboard resulted in error