detecting case-insensitivity

["J. Bruce Fields" <bfields@xxxxxxxxxxxx>]

Is there a generic way to detect whether a given filesystem is
case-insensitive?  If not, how should it be done?  (A bit in s_flags?)

(Somebody recently pointed out to me that NFSv4 has a "case_insensitive"
attribute, which we aren't currently returning a sensible value for.)

--b.