Make some xlogreader messages more accurate

Applying: Improve various error messages
Using index info to reconstruct a base tree...
M	src/backend/access/transam/twophase.c
M	src/backend/access/transam/xlogreader.c
M	src/backend/access/transam/xlogrecovery.c
M	src/backend/postmaster/postmaster.c
M	src/backend/replication/logical/worker.c
M	src/backend/statistics/mcv.c
M	src/backend/utils/adt/network.c
M	src/backend/utils/adt/tsquery.c
M	src/backend/utils/adt/tsvector.c
M	src/backend/utils/adt/varbit.c
M	src/pl/plpython/expected/plpython_types.out
M	src/pl/plpython/plpy_typeio.c
M	src/test/modules/test_rbtree/test_rbtree.c
Falling back to patching base and 3-way merge...
Auto-merging src/test/modules/test_rbtree/test_rbtree.c
Auto-merging src/pl/plpython/plpy_typeio.c
CONFLICT (content): Merge conflict in src/pl/plpython/plpy_typeio.c
Auto-merging src/pl/plpython/expected/plpython_types.out
CONFLICT (content): Merge conflict in src/pl/plpython/expected/plpython_types.out
Auto-merging src/backend/utils/adt/varbit.c
Auto-merging src/backend/utils/adt/tsvector.c
CONFLICT (content): Merge conflict in src/backend/utils/adt/tsvector.c
Auto-merging src/backend/utils/adt/tsquery.c
Auto-merging src/backend/utils/adt/network.c
Auto-merging src/backend/statistics/mcv.c
Auto-merging src/backend/replication/logical/worker.c
Auto-merging src/backend/postmaster/postmaster.c
CONFLICT (content): Merge conflict in src/backend/postmaster/postmaster.c
Auto-merging src/backend/access/transam/xlogrecovery.c
Auto-merging src/backend/access/transam/xlogreader.c
CONFLICT (content): Merge conflict in src/backend/access/transam/xlogreader.c
Auto-merging src/backend/access/transam/twophase.c
Patch failed at 0001 Improve various error messages

error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"