os: implement waitable management.

This implements waitable management for Events (and
implements Events). It also refactors PM to use new
Event/Waitable semantics, and also adds STS_ASSERT
as a macro for asserting a boolean expression. The
rest of stratosphere has been refactored to use
STS_ASSERT whenever possible.

stratosphere/libstratosphere/include/stratosphere.hpp

@@ -21,13 +21,9 @@
 #include "stratosphere/utilities.hpp"
 #include "stratosphere/emummc_utilities.hpp"
 
-#include "stratosphere/scope_guard.hpp"
-
 #include "stratosphere/version_check.hpp"
 
-#include "stratosphere/auto_handle.hpp"
 #include "stratosphere/iwaitable.hpp"
-#include "stratosphere/event.hpp"
 
 #include "stratosphere/waitable_manager.hpp"