man: move more examples to stand-alone files and use 2-space indentation consistenty

man: move more examples to stand-alone files and use 2-space indentation consistenty

Moving them out makes it easier to run them through a compiler, use automatic
indentation, and opens the possibility to provide a download link in the
future. I verified that all examples compile cleanly.

(2-space indentation is used because the examples are already significantly
indented in the man page, and we need to keep them narrow so that they display
well on standard terminals.)