fileutils.rb: remove code for OS/2 emx

* lib/fileutils.rb (FileUtils#mv): remove code for OS/2 emx, its
  support has been dropped yeas ago.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63440 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Author: nobu

lib/fileutils.rb

@@ -523,8 +523,6 @@ def mv(src, dest, force: nil, noop: nil, verbose: nil, secure: nil)
         if destent.exist?
           if destent.directory?
             raise Errno::EEXIST, d
-          else
-            destent.remove_file if rename_cannot_overwrite_file?
           end
         end
         begin
@@ -547,15 +545,6 @@ def mv(src, dest, force: nil, noop: nil, verbose: nil, secure: nil)
   alias move mv
   module_function :move
 
-  def rename_cannot_overwrite_file?   #:nodoc:
-    if defined?(RbConfig)
-      /emx/ =~ RbConfig::CONFIG['host_os']
-    else
-      /emx/ =~ RUBY_PLATFORM
-    end
-  end
-  private_module_function :rename_cannot_overwrite_file?
-
   #
   # Remove file(s) specified in +list+.  This method cannot remove directories.
   # All StandardErrors are ignored when the :force option is set.