Log Message:
-----------
Mention that the archive history file has the wal start/stop file names.
Modified Files:
--------------
pgsql/doc/src/sgml:
backup.sgml (r2.76 -> r2.77)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/backup.sgml.diff?r1=2.76&r2=2.77)