.dev files?

Some background:

When I typically upgrade to a new version, I make some changes to the code package before it gets upgraded. I’m not really sure if I need to do this anymore, but I do it since it still works.

I basically make two changes, one to pluggable.php so that any comments are always sent to the author and to me (multiple authors).

The second change is that I update quicktags.js so that when I add an image, an extra prompt comes up asking me if I want the image to be aligned left/right/centered. This allows the CSS to key off the alignment for my posts.

This time in loading 2.8, I noticed a quicktags.js and a quicktags.dev.js. From what I can tell, quicktags.js has no code formatting so it’s practially impossible to add any code. However, quicktags.dev.js does, so I added it to the .dev file, and then renamed it to quicktags.js. This allows my extra prompt to show up, but I was wondering do I need both a .dev file and the original .js file?

Is there another way to do this, or is what I did fine? Everything seems to work normally as far as I can tell.

Thanks for any help!