Fix pg_type.typlen for newly-revived line type.

Commit 261c7d4b removed the "m" field
from struct LINE, but neglected to make pg_type.h's idea of the type's
size match.  This resulted in reading past the end of palloc'd LINE
values when inserting them into tuples etc.  In principle that could
cause a SIGSEGV, though the odds of detectable problems seem low.

Bump catversion since this makes an incompatible on-disk format change.
Note that if the line type had been in use in the field, this would
break pg_upgrade'ability of databases containing line values; but
it seems unlikely that there are any (they'd have had to be compiled
with -DENABLE_LINE_TYPE).

Spotted by Andres Freund.