htc: declare and begin impl of HtclowManagerImpl interface

libraries/libstratosphere/source/htclow/driver/htclow_driver_manager.cpp

@@ -59,4 +59,9 @@ namespace ams::htclow::driver {
         return m_open_driver;
     }
 
+    void DriverManager::SetDebugDriver(IDriver *driver) {
+        m_debug_driver = driver;
+        m_driver_type  = impl::DriverType::Debug;
+    }
+
 }

libraries/libstratosphere/source/htclow/driver/htclow_driver_manager.hpp

@@ -35,6 +35,8 @@ namespace ams::htclow::driver {
             Result OpenDriver(impl::DriverType driver_type);
 
             IDriver *GetCurrentDriver();
+
+            void SetDebugDriver(IDriver *driver);
     };
 
 }