Add tablespace tap test to pg_rewind

Hi hackers,

There is already a databases tap tests in pg_rewind, wonder if there is a
need for tablespace tap tests in pg_rewind.
Attached is a initial patch from me.

Here is a patch for runing pg_rewind, it is very similar to
src/bin/pg_rewind/t/002_databases.pl, but there is no master_psql("CREATE
TABLESPACE beforepromotion LOCATION '$tempdir/beforepromotion'"); after
create_standby() and before promote_standby(), because pg_rewind will error
out :
could not create directory
"/Users/sbai/work/postgres/src/bin/pg_rewind/tmp_check/t_006_tablespace_master_local_data/pgdata/pg_tblspc/24576/PG_12_201903063":
File exists
Failure, exiting

The patch is created on top of the
commit e1e0e8d58c5c70da92e36cb9d59c2f7ecf839e00 (origin/master, origin/HEAD)
Author: Michael Paquier <michael(at)paquier(dot)xyz>
Date: Fri Mar 8 15:10:14 2019 +0900

Fix function signatures of pageinspect in documentation

tuple_data_split() lacked the type of the first argument, and
heap_page_item_attrs() has reversed the first and second argument,
with the bytea argument using an incorrect name.

Author: Laurenz Albe
Discussion:
https://postgr.es/m/8f9ab7b16daf623e87eeef5203a4ffc0dece8dfd.camel@cybertec.at
Backpatch-through: 9.6