io.c: opening external command
From: Nobuyoshi Nakada nobu@ruby-lang.org
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61317 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
io.c: opening external command
as other than IO singleton method, probably unintentionally,
warn if it is File or raise ArgumentError.
From: Nobuyoshi Nakada nobu@ruby-lang.org
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61317 b2dd03c8-39d4-4d8f-98ff-823fe69b080e