Fix some minor typos

[yoshikazusawa]

I found a few small minor typos, so I'll send this patch.

[ap]

I like this but would personally be inclined to throw in a

*_replacment_path = \&_replacement_path; # backcompat shim

just in case anyone is calling this method, despite the fact that it’s private and undocumented. Or alternatively at least call out the rename in the changelog. @xdg?

[xdg]

I'm fine without the shim. Thank you for the PR.

[yoshikazusawa]

@ap Thank you for your suggestion!
@xdg Thank you!