= sign in url breaks editing

I have an image that has a link to a url with ?key=value. The filter-tag parsing causes this to be parsed incorrectly in tinymce. The = in my url and everything after are truncated on page load, so that if I save, the mistake is propogated to the database.

I have a fix.

This fix works in 5.x-1.8. Now, according to #304869: Equal sign in macro parameter value breaks rendered display, this problem also exists in 6.x-2.x-dev, but I looked at the code of 6.x-2.0-alpha4, and it uses an approach similar to mine. So either it has been fixed in 6.x-2.0 since that post was made, or the differences between my approach and the one there are enough to break it.

So, this patch works in 5.x-1.8. I didn't test 6.x-2.0, but if that's still broken, this approach could be considered for that as well.