Comments inside quote characters get marked as cke_protected

[Lyuba]

To reproduce:

1. Switch to the source mode of a clean editor and enter the following text:

   <p>a'b <!--comment--> c'd</p>
   <p>ab <!--comment--> cd</p>
   

2. Now switch back to WYSIWYG mode, and see that the comment in the first line has been marked up as cke_protected, while the second one did not:

   a'b {cke_protected_1} c'd
   ab cd
   

Expected: The comment blocks should behave the same way regardless of quote characters around them, I would expect neither of them to be marked up as protected.

[Jakub Ś]

DUP of #8216.

There is also #9205 which has patch for this problem.