[ci skip] DocBlocks for DB drivers' utility classes

Partially fixes issue #1295.
diff --git a/system/database/drivers/oci8/oci8_forge.php b/system/database/drivers/oci8/oci8_forge.php
index fed8141..ad578f8 100644
--- a/system/database/drivers/oci8/oci8_forge.php
+++ b/system/database/drivers/oci8/oci8_forge.php
@@ -35,10 +35,29 @@
  */
 class CI_DB_oci8_forge extends CI_DB_forge {
 
+	/**
+	 * CREATE DATABASE statement
+	 *
+	 * @var	string
+	 */
 	protected $_create_database	= FALSE;
+
+	/**
+	 * DROP DATABASE statement
+	 *
+	 * @var	string
+	 */
 	protected $_drop_database	= FALSE;
+
+	/**
+	 * DROP TABLE statement
+	 *
+	 * @var	string
+	 */
 	protected $_drop_table		= 'DROP TABLE %s';
 
+	// --------------------------------------------------------------------
+
 	/**
 	 * Create Table
 	 *