The file format for each option now features a "Example:" header that
can provide one or more examples that get rendered appropriately in the
output. All options MUST have at least one example or gen.pl complains
at build-time.
This fix also does a few other minor format and consistency cleanups.
Closes#7654
Since --cookie-jar is the preferred way to store cookies, no longer
suggest using --dump-header to do so.
Co-authored-by: Daniel Stenberg
Closes https://github.com/curl/curl/issues/7414
