* lib/logger.rb (Logger::Period#previous_period_end): as weekly
rotation shifts the log file on Sundays, the end date of the
previous period should be Saturdays. fix r45072.
[ruby-dev:49314] [Bug #11622]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52297 b2dd03c8-39d4-4d8f-98ff-823fe69b080e