DEVEL15-windows-osi-convertRToW-and-logging-optimizations-20080227

DEVEL15-windows-osi-convertRToW-and-logging-optimizations-20080227

LICENSE MIT

Add lock_convertRToW which permits a read-lock to be upgraded to a
write lock.  If the caller is the only reader it permits a fast
transition otherwise it adds the caller to the waiters queue.

In the osi_Log macros, check to see if the log is enabled before making
the function call.  This avoids significant function call overhead.

In the cache manager, make use of the above.

(cherry picked from commit 72687c02b6ee5ff3029937b0278733b252f14550)