io.c: read BOM only for reading
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60884 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
io.c: read BOM only for reading
unless opened for reading.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60884 b2dd03c8-39d4-4d8f-98ff-823fe69b080e