Fix -Wimplicit-fallthrough

storage/innobase/include/data0type.ic

 /*****************************************************************************
 
 Copyright (c) 1996, 2012, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2018, MariaDB Corporation.
+Copyright (c) 2018, 2019, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -427,6 +427,7 @@ dtype_get_fixed_size_low(
 			return(0);
 		}
 #endif /* UNIV_DEBUG */
+		/* fall through */
 	case DATA_CHAR:
 	case DATA_FIXBINARY:
 	case DATA_INT:
@@ -503,6 +504,7 @@ dtype_get_min_size_low(
 			return(0);
 		}
 #endif /* UNIV_DEBUG */
+		/* fall through */
 	case DATA_CHAR:
 	case DATA_FIXBINARY:
 	case DATA_INT: