Log Message:
-----------
Document possible problems with NFS tablespaces.
Modified Files:
--------------
pgsql/doc/src/sgml:
manage-ag.sgml (r2.55 -> r2.56)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/manage-ag.sgml?r1=2.55&r2=2.56)