assets/revision: Fix a couple of bugs related to events handling
When browsing a content through the revision view, the click event handlers
for highlighting content lines or diff lines in the Changes tab were in
conflict leading to weird GUI behavior. So ensure each click handler is
executed only when needed.
Also modifying URL fragment when resetting diff highlighting triggers the
hashchange handler for code highlighting so avoid processing the fragment
if it does not match line numbers regexp.
Finally, prevent unwanted document scrolling when modifying URL fragment
after the cancellation of diff highlighting.