Switch from interprocess_shared_mutex to interprocess_upgradable_mutex.
Switch from interprocess_shared_mutex to interprocess_upgradable_mutex.

The former was only introduced in Boost 1.52, and we can't bump the
dep that far yet (for reference, Wheezy and Precise are both on 1.49)

Armada651/OSVR-Core,Armada651/OSVR-Core,feilen/OSVR-Core,leemichaelRazer/OSVR-Core,feilen/OSVR-Core,feilen/OSVR-Core,godbyk/OSVR-Core,OSVR/OSVR-Core,leemichaelRazer/OSVR-Core,d235j/OSVR-Core,godbyk/OSVR-Core,feilen/OSVR-Core,OSVR/OSVR-Core,Armada651/OSVR-Core,godbyk/OSVR-Core,leemichaelRazer/OSVR-Core,leemichaelRazer/OSVR-Core,godbyk/OSVR-Core,godbyk/OSVR-Core,d235j/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,Armada651/OSVR-Core,feilen/OSVR-Core,d235j/OSVR-Core,OSVR/OSVR-Core,d235j/OSVR-Core,d235j/OSVR-Core,Armada651/OSVR-Core,leemichaelRazer/OSVR-Core,godbyk/OSVR-Core,OSVR/OSVR-Core