adjust docstring formatting

[riscy]

Frequent user of this package -- thanks a lot.

Here are a few adjustments I made to the docstrings that might be worth merging. In many cases the appearance of the documentation in M-x apropos is improved, and in the cases where I de-indented comments, the appearance of the documentation in M-x help is improved.

I used https://www.gnu.org/software/emacs/manual/html_node/elisp/Documentation-Tips.html and the built-in Emacs syntax checking as guides.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nikomatsakis (or someone else) soon.

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[nikomatsakis]

Seems good =)

[tromey]

Thanks for doing this. BTW if you don't know you can also try M-x checkdoc. IIRC sometimes it's a bit too pedantic, but occasionally worth checking out.