to be a hierarchical-list-item<%> object, but now it is
a list of language names (same information, different data)
and one place didn't get updated.
Closes PR 12462
Specifically, in the case that we're inheriting a language setting
from some earlier preference or something and the language we're
inheriting is one that saves prefixes, and the current file being
opened does not match any of the possible prefixes, then revert
to the not-a-language language, instead of using the value from
the preference
Also: finish the removal of the EoPL language level from the
DrRacket langauge dialog, and clean up the 'get guidance' dialog
Please cherrypick this commit to the 5.2 release branch
being edited in DrRacket (via places)
Added an API to let tools have access to that
information (and compute more stuff)
Used that to make an online version of Check Syntax
which led to a separately callable Check Syntax API.