Merge pull request #23 from HuiLi/master

合并更新
Merge pull request #24 from HuiLi/master

合并更新
update vdbe.c

update Opcode: Transaction, OpenRead, OpenWrite, VerifyCookie,
SetCookie, ReadCookie
Merge pull request #25 from HuiLi/master

合并更新
Merge pull request #56 from MinfeiZhou/master

update vdbe.c