use correct mime type for stats link, not often used yet.
fixup the 200/206 handling for streams and files

It seems that iphones do not like a 206 response when they send that range
request of 0-1 or 0-xxxx so don't.   For now, when dealing with streams, do
not send back a partial content response.
avoid spin lock test for BSD, allow for fallback to mutexes

spin locks are used for very short lived sections and has been working
nicely but there has been one report on FBSD showing corruption however
it works fine when mutexes are used instead.

The cause is unclear so for now, drop the spin lock test on BSD
builds