DANGER DANGER. Switching to global critical region.

This changes almost all locks held by guest threads to use a single global
critical region. This emulates the behavior on the PPC of disabling
interrupts (by calls like KeRaiseIrqlToDpcLevel or masking interrupts),
and prevents deadlocks from occuring when threads are suspended or
otherwise blocked.
This has performance implications and a pass is needed to ensure the
locking is as granular as possible. It could also break everything
because it's fundamentally unsound. We'll see.

src/xenia/apu/audio_system.h

@@ -11,9 +11,9 @@
 #define XENIA_APU_AUDIO_SYSTEM_H_
 
 #include <atomic>
-#include <mutex>
 #include <queue>
 
+#include "xenia/base/mutex.h"
 #include "xenia/base/threading.h"
 #include "xenia/cpu/processor.h"
 #include "xenia/kernel/objects/xthread.h"
@@ -67,10 +67,8 @@ class AudioSystem {
   std::atomic<bool> worker_running_ = {false};
   kernel::object_ref<kernel::XHostThread> worker_thread_;
 
-  xe::mutex lock_;
-
+  xe::global_critical_region global_critical_region_;
   static const size_t kMaximumClientCount = 8;
-
   struct {
     AudioDriver* driver;
     uint32_t callback;