Remove 'autoinit' DB setting

It doesn't make sense to do a load->database() call
but not connect to the database. IIRC there was more
stuff in CI_DB_driver::initialize() at some point,
so that was probably the reason why the setting
existed in the first place. However, now it only
results in users making invalid bug reports because
they don't understand the feature ...

Examples during just the past 2 weeks: #3571 #3601 #3607
diff --git a/system/database/DB.php b/system/database/DB.php
index 8ea7ca6..c9660e4 100644
--- a/system/database/DB.php
+++ b/system/database/DB.php
@@ -213,10 +213,5 @@
 		}
 	}
 
-	if ($DB->autoinit === TRUE)
-	{
-		$DB->initialize();
-	}
-
 	return $DB;
 }
diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index bbe65b4..68e5a28 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -124,15 +124,6 @@
 	public $dbcollat		= 'utf8_general_ci';
 
 	/**
-	 * Auto-init flag
-	 *
-	 * Whether to automatically initialize the DB connection.
-	 *
-	 * @var	bool
-	 */
-	public $autoinit		= TRUE;
-
-	/**
 	 * Encryption flag/data
 	 *
 	 * @var	mixed
@@ -381,6 +372,7 @@
 			}
 		}
 
+		$this->initialize();
 		log_message('info', 'Database Driver Class Initialized');
 	}
 
diff --git a/system/database/drivers/cubrid/cubrid_driver.php b/system/database/drivers/cubrid/cubrid_driver.php
index 4021179..f80b4db 100644
--- a/system/database/drivers/cubrid/cubrid_driver.php
+++ b/system/database/drivers/cubrid/cubrid_driver.php
@@ -163,10 +163,6 @@
 		{
 			return $this->data_cache['version'];
 		}
-		elseif ( ! $this->conn_id)
-		{
-			$this->initialize();
-		}
 
 		return ( ! $this->conn_id OR ($version = cubrid_get_server_info($this->conn_id)) === FALSE)
 			? FALSE
diff --git a/system/database/drivers/mysql/mysql_driver.php b/system/database/drivers/mysql/mysql_driver.php
index f8e9b6d..df0f249 100644
--- a/system/database/drivers/mysql/mysql_driver.php
+++ b/system/database/drivers/mysql/mysql_driver.php
@@ -223,10 +223,6 @@
 		{
 			return $this->data_cache['version'];
 		}
-		elseif ( ! $this->conn_id)
-		{
-			$this->initialize();
-		}
 
 		if ( ! $this->conn_id OR ($version = mysql_get_server_info($this->conn_id)) === FALSE)
 		{
diff --git a/system/database/drivers/mysqli/mysqli_driver.php b/system/database/drivers/mysqli/mysqli_driver.php
index 22a8ba6..e953db0 100644
--- a/system/database/drivers/mysqli/mysqli_driver.php
+++ b/system/database/drivers/mysqli/mysqli_driver.php
@@ -204,10 +204,6 @@
 		{
 			return $this->data_cache['version'];
 		}
-		elseif ( ! $this->conn_id)
-		{
-			$this->initialize();
-		}
 
 		return $this->data_cache['version'] = $this->conn_id->server_info;
 	}
diff --git a/system/database/drivers/oci8/oci8_driver.php b/system/database/drivers/oci8/oci8_driver.php
index b87b411..4010995 100644
--- a/system/database/drivers/oci8/oci8_driver.php
+++ b/system/database/drivers/oci8/oci8_driver.php
@@ -243,10 +243,6 @@
 		{
 			return $this->data_cache['version'];
 		}
-		elseif ( ! $this->conn_id)
-		{
-			$this->initialize();
-		}
 
 		if ( ! $this->conn_id OR ($version = oci_server_version($this->conn_id)) === FALSE)
 		{
diff --git a/system/database/drivers/pdo/pdo_driver.php b/system/database/drivers/pdo/pdo_driver.php
index 68aeb0e..cc77e95 100644
--- a/system/database/drivers/pdo/pdo_driver.php
+++ b/system/database/drivers/pdo/pdo_driver.php
@@ -156,10 +156,6 @@
 		{
 			return $this->data_cache['version'];
 		}
-		elseif ( ! $this->conn_id)
-		{
-			$this->initialize();
-		}
 
 		// Not all subdrivers support the getAttribute() method
 		try
diff --git a/system/database/drivers/postgre/postgre_driver.php b/system/database/drivers/postgre/postgre_driver.php
index 3f3e3f0..7be07c3 100644
--- a/system/database/drivers/postgre/postgre_driver.php
+++ b/system/database/drivers/postgre/postgre_driver.php
@@ -213,10 +213,6 @@
 		{
 			return $this->data_cache['version'];
 		}
-		elseif ( ! $this->conn_id)
-		{
-			$this->initialize();
-		}
 
 		if ( ! $this->conn_id OR ($pg_version = pg_version($this->conn_id)) === FALSE)
 		{
diff --git a/system/database/drivers/sqlsrv/sqlsrv_driver.php b/system/database/drivers/sqlsrv/sqlsrv_driver.php
index 8f17c8f..16f77fa 100644
--- a/system/database/drivers/sqlsrv/sqlsrv_driver.php
+++ b/system/database/drivers/sqlsrv/sqlsrv_driver.php
@@ -292,10 +292,6 @@
 		{
 			return $this->data_cache['version'];
 		}
-		elseif ( ! $this->conn_id)
-		{
-			$this->initialize();
-		}
 
 		if ( ! $this->conn_id OR ($info = sqlsrv_server_info($this->conn_id)) === FALSE)
 		{
diff --git a/system/libraries/Session/drivers/Session_database_driver.php b/system/libraries/Session/drivers/Session_database_driver.php
index 20cec00..f496b4f 100644
--- a/system/libraries/Session/drivers/Session_database_driver.php
+++ b/system/libraries/Session/drivers/Session_database_driver.php
@@ -122,7 +122,7 @@
 	public function open($save_path, $name)
 	{
 		return empty($this->_db->conn_id)
-			? ( ! $this->_db->autoinit && $this->_db->db_connect())
+			? (bool) $this->_db->db_connect()
 			: TRUE;
 	}