Remotery: Minor comment cleanup.
Remotery: Fix startup race condition with Remotery sampling itself.
The Remotery thread would use rmt_BeginCPUSample/etc to monitor itself. rmt_BeginCPUSample returns if g_Remotery is not set. g_Remotery only gets set *after* Remotery has been successfully initialised, however the Remotery thread is launched before that.
Moved global instance management into Remotery_Create itself and explicitly set it before launching the Remotery thread.