Adding `USEMODULE += core_mutex_debug` to your `Makefile` results in
on log messages such as
[mutex] waiting for thread 1 (pc = 0x800024d)
being added whenever `mutex_lock()` blocks. This makes tracing down
deadlocks easier.
This is intended for the bootloader module where we don't enter thread
mode, so mutex must never attempt to switch context.
Instead use a simple busy wait that is enough to make the possible mutex
users (e.g. interrupt based SPI) in bootloader mode work.
Separate thread names from DEVELHELP so thread names can be
enabled in non-development/debug builds when required/desired.
THREAD_NAMES will be enabled by default then DEVELHELP is set to 1.
