android: prepare simplified utf support

Add some missing mb funcs and mbtest app

Change-Id: Ib80ee94d0dad6bf91df780c43fdce6694a4e3d19

Signed-off-by: Tanguy Pruvot <tanguy.pruvot@gmail.com>
update config.h

Change-Id: I4f0471936a95075f74f3c8c87ab44023c0471755
add some mbtowc/wctomb tests

Change-Id: Id18ef71de355b8d316feafa6383f9bacd828a7fa
fix some type warnings

Change-Id: Ifb153429f8129e4da35d7e3c3186e674e7330f8d