nXML mode word separators

[Skip Montanaro <skip.montanaro@gmail.com>]

I unfortunately have to work with handwritten XML which is used to
define complex application configs. In that context, apostrophes are
valid string delimiters, at least in whatever XML pseudo-dialect these
files are written in. So, both of these snippets mean the same thing:

<Env INST="2" />
<Env INST='2' />

I'm not in any sort of position to dictate any changes, so I need to
adapt. So, forward-word currently skips over apostrophes (considering
them word characters) and kill-word (even worse) deletes them. It has
probably been a decade since I fiddled with syntax tables. How do I
move apostrophes from word class to quotation(?) class in the relevant
syntax table? FWIW, when editing XML files I seem to be in nxml-mode
(nothing I enabled specifically, must just be the default mode).

Thanks,

Skip Montanaro