Teletype 2.0 changes

[samdoshi]

Mainly just some small additions and changes.

1. Initialise app_event_handlers to be an array of handler_Ignore, which means that unhandled events will not cause crashes

2. Add events and support for USB memory sticks

3. Add timer pause and resume functions

Plus some other smaller tweaks.

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Unfortunately this breaks all the modules, due to none of them compiling msc.c or being able to find msc.h.

Here are the PRs to fix that:

• Teletype: monome/teletype#73
• Ansible: monome/ansible#24

I'll do the Trilogy modules once this, the Teletype and the Ansible changes are merged.

[ngwese]

If I'm understanding things correctly the changes to timers_pause/resume now disable both app and ui priority interrupts. The gives me the impression that we are no longer really making a distinction between app and ui?

This change is safe in that it is more protective than needed but the blurring of app and ui priority levels might be undesirable if/when the aleph codebase is moved to libavr32 (the seems to be some movement on that).

[samdoshi]

timers_pause / timers_resume only work with APP_TC_IRQ_PRIORITY. It's just that they track nested levels too.

The major bug fix is really in timers_remove, the early return in it doesn't re-enable the timer.

[samdoshi]

Just a bit more info, the inspiration for the fix is from your fix to the Aleph codebase, but's just for timers. More here