fix build warnings under VS
fix build warnings under VS

shanshan1026/sqlcipher,hongbinz/sqlcipher,Mozhuowen/sqlcipher,luis-allan/sqlcipher,ylfonline/sqlcipher,ylfonline/sqlcipher,shanshan1026/sqlcipher,pandazheng/sqlcipher,pandazheng/sqlcipher,RAN-II/sqlcipher,emodeqidao/sqlcipher,luis-allan/sqlcipher,shanshan1026/sqlcipher,Mozhuowen/sqlcipher,supriyantomaftuh/sqlcipher,cnbin/sqlcipher,luis-allan/sqlcipher,supriyantomaftuh/sqlcipher,pandazheng/sqlcipher,bestofsong/sqlcipher,RAN-II/sqlcipher,cnbin/sqlcipher,ylfonline/sqlcipher,RAN-II/sqlcipher,cnbin/sqlcipher,shanshan1026/sqlcipher,emodeqidao/sqlcipher,supriyantomaftuh/sqlcipher,bestofsong/sqlcipher,hongbinz/sqlcipher,emodeqidao/sqlcipher,hongbinz/sqlcipher,bestofsong/sqlcipher,Mozhuowen/sqlcipher