pgsql: Refactor replication connection code of various pg_basebackup ut

Refactor replication connection code of various pg_basebackup utilities.

Move some more code to manage replication connection command to
streamutil.c. A later patch will introduce replication slot via
pg_receivexlog and this avoid duplicating relevant code between
pg_receivexlog and pg_recvlogical.

Author: Michael Paquier, with some editing by me.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/0c013e08cfbebd35ec982c4df15d44b521094d52

Modified Files
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src/bin/pg_basebackup/pg_basebackup.c  |   21 +---
src/bin/pg_basebackup/pg_receivexlog.c |   38 ++-----
src/bin/pg_basebackup/pg_recvlogical.c |  116 +++++----------------
src/bin/pg_basebackup/streamutil.c     |  177 +++++++++++++++++++++++++++++++-
src/bin/pg_basebackup/streamutil.h     |   11 ++
5 files changed, 222 insertions(+), 141 deletions(-)