Renamed some functions

- Renamed Begin3dMode() --> BeginMode3D()
- Renamed Begin2dMode() --> BeginMode2D()
- Renamed End3dMode() --> EndMode3D()
- Renamed End2dMode() --> EndMode2D()

examples/models/models_skybox.c

@@ -60,13 +60,13 @@ int main()
 
             ClearBackground(RAYWHITE);
 
-            Begin3dMode(camera);
+            BeginMode3D(camera);
 
                 DrawModel(skybox, (Vector3){0, 0, 0}, 1.0f, WHITE);
                 
                 DrawGrid(10, 1.0f);
 
-            End3dMode();
+            EndMode3D();
 
             DrawFPS(10, 10);