Hubris user library for tasks

This crate provides the Hubris system call interface and assorted utility code for use in task programs.

Crate features

• panic-messages: on panic!, attempt to record the panic message in unused stack space so the supervisor can extract it. This has an impact on both binary size and worst-case stack usage. Generally this feature should only be set in the top-level task, not in libraries.

• log-itm / log-semihosting: select one of two backends for the log! macros. If you provide neither, the log macros won't compile.