Activities tab empty and showing "Processing" when an activity subject contains tab, newline or vertical tab

We've had reports of certain contacts' Activities tabs being empty and showing "Processing", despite the contact having activities. This has occurred on 3 different sites, most recently on 4.1.2 . We found that the problem occurred when one of the activities had a subject containing a tab, newline or vertical tab character. The attached patch fixes this for the activities tab by filtering out these characters.

Spurious characters can cause problems in other contexts too - e.g. we had an issue with what I think was a "smart" quote or similar pasted from Word in a CiviMail subject, causing a mailing to break dramatically. Perhaps it makes sense to sanitise this sort of thing on input as well as / instead of on output.