general: Use deducation guides for std::lock_guard and std::unique_lock

Since C++17, the introduction of deduction guides for locking facilities
means that we no longer need to hardcode the mutex type into the locks
themselves, making it easier to switch mutex types, should it ever be
necessary in the future.

src/input_common/motion_emu.cpp

@@ -39,7 +39,7 @@ public:
     void Tilt(int x, int y) {
         auto mouse_move = Common::MakeVec(x, y) - mouse_origin;
         if (is_tilting) {
-            std::lock_guard<std::mutex> guard(tilt_mutex);
+            std::lock_guard guard{tilt_mutex};
             if (mouse_move.x == 0 && mouse_move.y == 0) {
                 tilt_angle = 0;
             } else {
@@ -51,13 +51,13 @@ public:
     }
 
     void EndTilt() {
-        std::lock_guard<std::mutex> guard(tilt_mutex);
+        std::lock_guard guard{tilt_mutex};
         tilt_angle = 0;
         is_tilting = false;
     }
 
     std::tuple<Common::Vec3<float>, Common::Vec3<float>> GetStatus() {
-        std::lock_guard<std::mutex> guard(status_mutex);
+        std::lock_guard guard{status_mutex};
         return status;
     }
 
@@ -93,7 +93,7 @@ private:
             old_q = q;
 
             {
-                std::lock_guard<std::mutex> guard(tilt_mutex);
+                std::lock_guard guard{tilt_mutex};
 
                 // Find the quaternion describing current 3DS tilting
                 q = Common::MakeQuaternion(
@@ -115,7 +115,7 @@ private:
 
             // Update the sensor state
             {
-                std::lock_guard<std::mutex> guard(status_mutex);
+                std::lock_guard guard{status_mutex};
                 status = std::make_tuple(gravity, angular_rate);
             }
         }