Use template specialization for uint8_t
Use template specialization for uint8_t

Visual Studio 2015 (v140) compiler failed build
because std::uniform_int_distribution cannot use uint8_t that is used as
cost_type.
See: https://faithandbrave.hateblo.jp/entry/2014/03/14/141928

fixstars-jp/libSGM,fixstars/libSGM