read mysql bit type as i64

[Cabbagec]

Currently, mysql column type MYSQL_TYPE_BIT is not supported, panicking the process if present in the table. And this issue is also stated in #359 and #491 .

I think it's appropriate to convert the bit type as longlong i64. According to the mysql doc page, bit type columns can store M-bit values, with M ranging from 1 to 64.

[wangxiaoying]

Thanks @Cabbagec for the PR! Since it's a new type, can you also add it to our unit test? You can add a new column and insert some values in the mysql table defined here, and modify the unit corresponding tests here.

[Cabbagec]

Thanks @Cabbagec for the PR! Since it's a new type, can you also add it to our unit test? You can add a new column and insert some values in the mysql table defined here, and modify the unit corresponding tests here.

Sure, will do later.