Log Message:
-----------
Don't allow pg_start_backup() to be invoked if archive_command has not
been defined. Patch from Gavin Sherry, editorializing by Neil Conway.
Modified Files:
--------------
pgsql/src/backend/access/transam:
xlog.c (r1.176 -> r1.177)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlog.c.diff?r1=1.176&r2=1.177)