Ruby

• thread.c (rb_thread_priority, rb_thread_priority_set): fix rdoc.
  Lower-priority thread may run even if there are higher-priority
  threads. See [ruby-dev:40977].

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27351 b2dd03c8-39d4-4d8f-98ff-823fe69b080e