Shares in several major Canadian forestry companies closed down Wednesday after an analyst downgrade and lower-than-expected building permits for the crucial U.S. housing sector.  CIBC analyst Hamir Patel said in a note that the bank has reduced its outlook on the industry, including downgrades on Interfor Corp., Resolute Forest Products Inc., and West Fraser Timber Co., as concerns mount about U.S. housing, the Globe and Mail reported.  "With more warnings signs flashing in the U.S. housing market ... we are now moving to the sidelines on all commodity wood product stock,” wrote ...