Pg 8.4.3 does not start up with "Permissions should be u=rwx (0700)

I upgraded from 8.4.2 to 8.4.3, and I couldn't start postgres. This was
printed on STDERR

FATAL:  data directory "path-to-my-data-dir" has group or world access
DETAIL:  Permissions should be u=rwx (0700).

This change was not documented in the release notes, and I don't think
permission != 700 should be a fatal error.  I purposely set o+x to let
any user be able to read the log files.