* doc/regexp.rdoc: [DOC] Clarify whitespace matching by @allolex
  [Fixes GH-606] https://github.com/ruby/ruby/pull/606 [ci skip]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46096 b2dd03c8-39d4-4d8f-98ff-823fe69b080e