improve man pages
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58411 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
improve man pages
fix document title formatting and volume name,
improve "REPORTING BUGS" section: fix mdoc formatting error
(wrong macro for bullet list items), small rewordings.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58411 b2dd03c8-39d4-4d8f-98ff-823fe69b080e