pgsql: Unify some tar functionality across different parts

Unify some tar functionality across different parts

Move some of the tar functionality that existed mostly duplicated
in both pg_dump and the walsender basebackup functionality into
port/tar.c instead, so it can be used from both. It will also be
used by pg_basebackup in the future, which would've caused a third
copy of it around.

Zoltan Boszormenyi and Magnus Hagander

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/f5d4bdd3a5c1b7987a257b2a64e977501338af0d

Modified Files
--------------
src/backend/replication/basebackup.c |  128 +-----------------------------
src/bin/pg_dump/pg_backup_tar.c      |  105 +------------------------
src/include/port.h                   |    4 +
src/port/Makefile                    |    2 +-
src/port/tar.c                       |  143 ++++++++++++++++++++++++++++++++++
5 files changed, 154 insertions(+), 228 deletions(-)