Fix use of va_list in QAndroidJniObject

va_list functions where update to work on x86 where va_list is defined
as char*.

Change-Id: If1286a36d766b8536ca9a83ca21791d30b7b307c
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>