This is like printf() but prints straight to the console instead of going
through the stdio library, the VFS and the device layer.

To be used for debugging outout in the kernel.

For musl code.

Running tests is now done by editing the command line in build.mak

With virtio we must use dynamic allocation for the correctness of
virt_to_phys

The tests themselves didn't change and all the changes their are just
changes of namespace usage and variable movement.

The EVENTHANDLER mechanism provides a way for kernel subsystems to register interest in kernel events and have their callback functions invoked when these events occur.

A console driver that wraps another with a spinlock.  We usually don't want
spinlocks, but if we want to debug the scheduler, we have to use them here.