Move all core types into namespaces (#1886)

* Reorganize namespaces

- Most types are now moved into the `melonDS` namespace
- Only good chance to do this for a while, since a big refactor is next

* Fix the build

src/frontend/duckstation/gl/context.h

@@ -6,6 +6,7 @@
 #include <vector>
 
 namespace GL {
+using namespace melonDS;
 class Context
 {
 public:

src/frontend/duckstation/gl/context_agl.h

@@ -13,6 +13,7 @@ struct NSView;
 
 namespace GL {
 
+using namespace melonDS;
 class ContextAGL final : public Context
 {
 public:

src/frontend/duckstation/gl/context_wgl.cpp

@@ -3,6 +3,7 @@
 #include "../log.h"
 #include "../scoped_guard.h"
 #include "loader.h"
+using namespace melonDS;
 Log_SetChannel(GL::ContextWGL);
 
 // TODO: get rid of this

src/frontend/duckstation/gl/x11_window.h

@@ -4,6 +4,7 @@
 #include <X11/Xutil.h>
 
 namespace GL {
+using namespace melonDS;
 class X11Window
 {
 public:

src/frontend/duckstation/window_info.h

@@ -28,8 +28,8 @@ struct WindowInfo
   Type type = Type::Surfaceless;
   void* display_connection = nullptr;
   void* window_handle = nullptr;
-  u32 surface_width = 0;
-  u32 surface_height = 0;
+  melonDS::u32 surface_width = 0;
+  melonDS::u32 surface_height = 0;
   float surface_refresh_rate = 0.0f;
   float surface_scale = 1.0f;
   SurfaceFormat surface_format = SurfaceFormat::RGB8;