Spelling errors/typos in method and field names

[tgvaughan]

Is there already a catch-all issue with which to associate commits that fix this kind of thing?

BTW, I'm aware that fixing this kind of thing willy-nilly (sp??) can break API backwards-compatibility, so of course care must be taken.

[rbouckaert]

Just added a fix to ensure old XML still runs, as discussed. Also, fixed consistent spelling error in member name :-)