If auto.assign is TRUE, the symbol will be written
to the environment specified in env with a
.div appended to the name.
If auto.update is TRUE and the object is of class
xts, the dividends will be included as an
attribute of the original object and be reassigned
to the environment specified by env.
All other cases will return the split data
as an xts object. NA is returned if there
is no split data.