Move the explanation for examples before the example itself. Add
numerous QEMU examples and explanations supplied by sbruno, with thanks
to Ingo Schwarze for help with the mdoc markup. Code, text, testing,
proofreading, cinematography, stunts, and the haunting theme song
supplied by sbruno.

Submitted by: sbruno
Reviewed by: sbruno
MFC after: 1 week