pgsql: Add -d option to pg_basebackup and pg_receivexlog, for connectio

Add -d option to pg_basebackup and pg_receivexlog, for connection string.

Without this, there's no way to pass arbitrary libpq connection parameters
to these applications. It's a bit strange that the option is called
-d/--dbname, when in fact you can *not* pass a database name in it, but it's
consistent with other client applications where a connection string is also
passed using -d.

Original patch by Amit Kapila, heavily modified by me.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/aa05c37e823a41056273e73f6b3d168009a67c3f

Modified Files
--------------
doc/src/sgml/ref/pg_basebackup.sgml | 17 ++++++
doc/src/sgml/ref/pg_receivexlog.sgml | 17 ++++++
src/bin/pg_basebackup/pg_basebackup.c | 7 ++-
src/bin/pg_basebackup/pg_receivexlog.c | 7 ++-
src/bin/pg_basebackup/streamutil.c | 87 +++++++++++++++++++++++--------
src/bin/pg_basebackup/streamutil.h | 1 +
6 files changed, 111 insertions(+), 25 deletions(-)