v/checker: Warn about pointer indexing outside unsafe {} (#5918)

vlib/os/os_windows.c.v

@@ -80,7 +80,7 @@ mut:
 fn init_os_args_wide(argc int, argv &byteptr) []string {
 	mut args := []string{}
 	for i in 0..argc {
-		args << string_from_wide(&u16(argv[i]))
+		args << string_from_wide(unsafe {&u16(argv[i])})
 	}
 	return args
 }