Introduce Streaming Replication.

This includes two new kinds of postmaster processes, walsenders and
walreceiver. Walreceiver is responsible for connecting to the primary server
and streaming WAL to disk, while walsender runs in the primary server and
streams WAL from disk to the client.

Documentation still needs work, but the basics are there. We will probably
pull the replication section to a new chapter later on, as well as the
sections describing file-based replication. But let's do that as a separate
patch, so that it's easier to see what has been added/changed. This patch
also adds a new section to the chapter about FE/BE protocol, documenting the
protocol used by walsender/walreceivxer.

Bump catalog version because of two new functions,
pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for
monitoring the progress of replication.

Fujii Masao, with additional hacking by me

doc/src/sgml/client-auth.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/client-auth.sgml,v 1.125 2009/12/12 21:35:21 mha Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/client-auth.sgml,v 1.126 2010/01/15 09:18:56 heikki Exp $ -->
 
 <chapter id="client-authentication">
  <title>Client Authentication</title>
@@ -181,6 +181,8 @@ hostnossl  <replaceable>database</replaceable>  <replaceable>user</replaceable>
        the requested user must be a member of the role with the same
        name as the requested database.  (<literal>samegroup</> is an
        obsolete but still accepted spelling of <literal>samerole</>.)
+       The value <literal>replication</> specifies that the record
+       matches if streaming replication is requested.
        Otherwise, this is the name of
        a specific <productname>PostgreSQL</productname> database.
        Multiple database names can be supplied by separating them with