remove native 'mysql_reconnect'

this native is impossible to implement with the system currently used, because connection data (host, username, password(!!), database) is internally not stored anymore (for the sake of security)
add first query related unit test
fix a bug where native 'mysql_errno' returned '0' (= no errors) when there is a connection failure

god bless unit tests
improve unit tests

- fixed indentation
- added raw check for query test suite
add another query unit test (basic result fetching)