Added stub for SwitchDesktop.

dlls/user/user32.spec

@@ -572,7 +572,7 @@
 @ stdcall ShowWindowAsync(long long)
 @ stdcall SubtractRect(ptr ptr ptr)
 @ stdcall SwapMouseButton(long)
-@ stub SwitchDesktop
+@ stdcall SwitchDesktop(long)
 @ stdcall SwitchToThisWindow(long long)
 # @ stub SysErrorBox
 @ stdcall SystemParametersInfoA(long long ptr long)

windows/win.c

@@ -3273,3 +3273,14 @@ BOOL WINAPI GetWindowInfo( HWND hwnd, PWINDOWINFO pwi)
 
     return TRUE;
 }
+
+/******************************************************************************
+ *              SwitchDesktop (USER32.@)
+ *
+ * NOTES: Sets the current input or interactive desktop.
+ */
+BOOL WINAPI SwitchDesktop( HDESK hDesktop)
+{
+    FIXME("SwitchDesktop(hwnd %p) stub!\n", hDesktop);
+    return TRUE;
+}