Fix integer overflow in utf{16,32}_to_utf8_length am: c17624db am:...

Fix integer overflow in utf{16,32}_to_utf8_length am: c17624db am: 3065de2c  -s ours am: c282fe5c  -s ours am: 47dfd5af  -s ours am: fc4b272a  -s ours am: 069ec60f  -s ours am: 3c374a2b  -s ours am: cee1faef  -s ours am: 8ecef89e  -s ours am: 78a6b7e2  -s ours am: 3560e921  -s ours
am: 173087ab  -s ours

Change-Id: Ic3204d08df1ec43c937734adb24bf0a28f5f03e9