Improve largeobject regression test to show size of object read from file.

The idea here is to provide a more easily diagnosable failure diff when
the problem is that tenk.data has been DOS-ified, as I believe to be
happening currently on buildfarm member hamerkop.  Per suggestion from
Magnus Hagander.

Also, sync output/largeobject_1.source with current regression test.
Failure to do that in commit 3a0e4d36eb
turns out to be the real reason that hamerkop has been complaining.

src/test/regress/input/largeobject.source

@@ -136,6 +136,9 @@ INSERT INTO lotest_stash_values (loid) SELECT lo_import('@abs_srcdir@/data/tenk.
 BEGIN;
 UPDATE lotest_stash_values SET fd=lo_open(loid, CAST(x'20000' | x'40000' AS integer));
 
+-- verify length of large object
+SELECT lo_lseek(fd, 0, 2) FROM lotest_stash_values;
+
 -- with the default BLKSZ, LOBLKSZ = 2048, so this positions us for a block
 -- edge case
 SELECT lo_lseek(fd, 2030, 0) FROM lotest_stash_values;