edits to eliminate byte-compilation warnings in emacs 28

[jmay]

This is purely to clear out warnings when emacs 28 aggressively attempts to byte-compile everything.

• split long docstrings
• added declare-function to avoid "not known to be defined" warnings
• moved alias above referent

[purcell]

Thanks for looking at this. Re. the long docstrings, this is not quite the correct fix, because those now make checkdoc unhappy. The right fix is usually to wordsmith the function descriptions until the first sentence is short enough. Extra info can go into subsequent sentences.

[jmay]

Cool, I never knew about this! I'll run this and apply all its recommendations.

[purcell]

Great, thanks — merged.