Driveby cleanup: Remove use of legacy <tchar.h>

Windows/MainWindow.cpp

@@ -153,7 +153,7 @@ namespace MainWindow
 	bool noFocusPause = false;	// TOGGLE_PAUSE state to override pause on lost focus
 	bool trapMouse = true; // Handles some special cases(alt+tab, win menu) when game is running and mouse is confined
 
-	static const TCHAR szWindowClass[] = L"PPSSPPWnd";
+	static constexpr wchar_t *szWindowClass = L"PPSSPPWnd";
 
 	static LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
 
@@ -174,7 +174,7 @@ namespace MainWindow
 		wcex.lpfnWndProc = (WNDPROC)WndProc;
 		wcex.hInstance = hInstance;
 		wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
-		wcex.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
+		wcex.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);  // or NULL?
 		wcex.lpszMenuName	= (LPCWSTR)IDR_MENU1;
 		wcex.lpszClassName = szWindowClass;
 		wcex.hIcon = LoadIcon(hInstance, (LPCTSTR)IDI_PPSSPP);