Allow wait_irq to be called in 32bit code.

Allow wait_irq to be called in 32bit code.

If wait_irq() is called from 32bit code, then jump to 16bit mode for
the wait.

Have wait_irq check for threads, and have it use yield if threads are
pending.  This ensures threads aren't delayed if anything calls
wait_irq.

Use wait_irq() in 32bit mode during a failed boot.