Create a built-in log rotation program, so that we no longer have to

recommend that people go get Apache's rotatelogs program.  Additional
benefits are that configuration is done through GUC, rather than
externally, and that the postmaster can monitor the log rotator and
restart it after failure (though we certainly hope that won't happen
often).
Andreas Pflug, some rework by Tom Lane.

src/backend/utils/misc/postgresql.conf.sample

@@ -170,9 +170,23 @@
 #log_destination = 'stderr'	# Valid values are combinations of stderr,
                                 # syslog and eventlog, depending on
                                 # platform.
+
+# This is relevant when logging to stderr:
+#redirect_stderr = false    # Enable capturing of stderr into log files.
+# These are only relevant if redirect_stderr is true:
+#log_directory = 'pg_log'   # Directory where logfiles are written.
+                            # May be specified absolute or relative to PGDATA
+#log_filename_prefix = 'postgresql_' # Prefix for logfile names.
+#log_rotation_age = 1440    # Automatic rotation of logfiles will happen after
+                            # so many minutes.  0 to disable.
+#log_rotation_size = 10240  # Automatic rotation of logfiles will happen after
+                            # so many kilobytes of log output.  0 to disable.
+
+# These are relevant when logging to syslog:
 #syslog_facility = 'LOCAL0'
 #syslog_ident = 'postgres'
 
+
 # - When to Log -
 
 #client_min_messages = notice	# Values, in order of decreasing detail: