Jason Song c84238800b
Refactor `setting.Database.UseXXX` to methods ()
Replace .

Refactor `setting.Database.UseMySQL` to
`setting.Database.Type.IsMySQL()`.

To avoid mismatching between `Type` and `UseXXX`.

This refactor can fix the bug mentioned in , so it should be
backported.
..
db.go Refactor `setting.Database.UseXXX` to methods ()
db_test.go
hash.go Use minio/sha256-simd for accelerated SHA256 ()
main_test.go
testlogger.go
tests.go Refactor the setting to make unit test easier ()