`FileTest.send(command, ...)` allows to call not only FileTest-related
methods but also any method that belongs to Kernel, Object, etc.
patched by <mame@ruby-lang.org>


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@67820 b2dd03c8-39d4-4d8f-98ff-823fe69b080e