Database: Add $allow_bail argument to wpdb::check_connection() to match the connect method. Fixes #41
PHPDoc fixes for functionality in wp-includes/wp-db.php added in 3.9. Fixes #43.
Rename USE_EXT_MYSQL to WP_USE_EXT_MYSQL. Fixes #44.
mprove inline documentation for the wpdb::$show_errors property.
Note that SQL/DB errors are displayed by default if both WP_DEBUG and WP_DEBUG_DISPLAY evaluate to true. Fixes #45.
In wpdb, remove dead code. Fixes #46.
In wpdb, make some things explicitly public. Do not set anything to private. This would instantly blow up hyperdb in the wild. Fixes  #47
LIKE escape sanity:
Deprecate like_escape()
Add a method to $wpdb, ->esc_like(), and add unit tests.

Fixes #49.