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.