[ruby/reline] Bypass cursor down when a char is rendered at eol on Windows

A newline is automatically inserted if a character is rendered at eol on
Windows command prompt.

4bfea07e4a

lib/reline/general_io.rb

@@ -5,6 +5,10 @@ class Reline::GeneralIO
     RUBY_PLATFORM =~ /mswin|mingw/ ? Encoding::UTF_8 : Encoding::default_external
   end
 
+  def self.win?
+    false
+  end
+
   RAW_KEYSTROKE_CONFIG = {}
 
   @@buf = []