Log Message:
Update ruby-mysql2 to 0.4.8.

0.4.7

* Adding support for MYSQL_ENABLE_CLEARTEXT_PLUGIN flag (#845)
* Avoid invalidating re-assigned socket fd by fixing connected check (#847)
* Wait for close to be processed by server in test for Threads_connected (#850)
* Fix flaky test that used Process.wait without specifying a pid (#849)
* Add a Mysql2::Client#closed? method (#796)
* Fix use after free of client field when closing with reconnect option (#846)
* Fix leaky test that caused a re-assigned socket to be closed on GC. (#853)
* Close several unclosed clients in tests (#848)
* Fix spec that expected Client#socket on all platforms, it's not available on
  WIndows
* Docs: Fix link in readme (#854)
* English grammar: Fix incorrect use of word "deprecated" (#855)
* Minimal required changes to make it work for mariadb 10.2 (#857)
* Fix segfault for Mysql2::Statement#fields on non-SELECT queries
* Fix for name change of struct NET.vio to .pvio in MariaDB Connector/C 3.x.
* Fix for MariaDB 10.2 which does not define CLIENT_LONG_PASSWORD
* Add README section to discuss the special meaning of localhost
* Move the section for Multple Result Sets
* Update MySQL Connector/C version for Windows
* Change the quoting for unzipping MySQL Connector/C for Windows

0.4.8

* Add ifdefs for MySQL 5.1 without MYSQL_ENABLE_CLEARTEXT_PLUGIN