For numerical input, including vectors, matrices and arrays,
lon360() simply calls ifelse() to add 360 to any negative values. For
'>section objects, it changes longitude in the metadata slot
and then calls itself to handle the '>ctd objects stored as
as the entries in station within the data slot.
For this '>ctd object, and indeed for all non-'>section
objects, lon360() changes longitude values in the
metadata slot (if present) and also in the data slot (again, if
present). This function is not useful for dealing with coastline
data; see coastlineCut() for such data.