driver: fixes missing driver.NamedValueChecker implementation

[micanzhang]

github.com/go-sql-driver/mysql
do implement its own CheckNamedValue which used at https://github.com/golang/go/blob/master/src/database/sql/convert.go#L129

[micanzhang]

@odeke-em PTAL

[odeke-em]

Thank you for this change @micanzhang! However, what if a database doesn't implement that method? This change will break code for other databases. Perhaps you can type assert on it. What's the utility though of adding it? Please explain why we should use it.

[micanzhang]

i make some updates when a database driver doesn't implement that interface then use database/sql's default column value convertor; since mysql driver has different implementation of value check, espiciallly for uint64 which supports by mysql driver but illegal when use database/sql

[micanzhang]

mysql driver:

• https://github.com/go-sql-driver/mysql/blob/master/connection.go#L631

• https://github.com/go-sql-driver/mysql/blob/46351a8892976898935f653f5333782579a96fa5/statement.go#L179

database/sql:

• https://github.com/golang/go/blob/master/src/database/sql/driver/types.go#L273

[odeke-em]

Gotcha, thank you @micanzhang and LGTM!