Fix tuptoaster bugs induced by making bytea toastable. Durn thing was

Fix tuptoaster bugs induced by making bytea toastable.  Durn thing was
trying to toast tuples inserted into toast tables!  Fix is two-pronged:
first, ensure all columns of a toast table are marked attstorage='p',
and second, alter the target chunk size so that it's less than the
threshold for trying to toast a tuple.  (Code tried to do that but the
expression was wrong.)  A few cosmetic cleanups in tuptoaster too.
NOTE: initdb forced due to change in toaster chunk-size.