So you can `go build -tags=jsoniter` to use `github.com/json-iterator/go` as default json handler
Fix#1744
Reviewed-on: https://gitea.com/xorm/xorm/pulls/1916
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-committed-by: Lunny Xiao <xiaolunwen@gmail.com>