Use Rex::Compat.getenv instead

Also, this would deprecate out the editor plugin.

Author: Tod Beardsley

lib/msf/ui/console/command_dispatcher/core.rb

@@ -629,7 +629,7 @@ def cmd_connect(*args)
   end
 
   def cmd_edit_help
-    editor = ENV['VISUAL'] || ENV['EDITOR']
+    editor = Rex::Compat.getenv('VISUAL') || Rex::Compat.getenv('EDITOR')
     msg = "Edit the currently active module"
     msg = "#{msg} #{editor ? "with #{editor}" : "($EDITOR must be set first)"}."
     print_line "Usage: edit"