* man/ri.1: update the (very outdated) ri man page:
  * update document date
  * fix document title formatting and volume name
  * update descriptions and options to current ri --help text
  * fix some mdoc formatting errors (missing escaping of `\',
    wrong macro for bullet list items)
  * various rewordings and other improvements

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58410 b2dd03c8-39d4-4d8f-98ff-823fe69b080e