SqString

Should we back out SqString for now until the implicit cast issues have
been analyzed in more detail, or try fixing it somehow for the 3.0
release?

http://www.squid-cache.org/bugs/show_bug.cgi?id=1970

My vote is to defer the SqString change to 3.1, or at least after 3.0
has been branched from HEAD.

Reasoning: More work is required to polish it, and it doesn't really add
anything to the 3.0 release (beyond the bugfixes it triggered
indirectly), mainly preparation for future work.

Regards
Henrik