UBSAN: Fix a bit shift overflow

Shifting a 16-bit type by 16 bits is undefined behaviour.
The result is at least 32 bits, so let us cast the shift operand
to a wider type before shifting.

sql-common/client.c

 /* Copyright (c) 2003, 2016, Oracle and/or its affiliates.
-   Copyright (c) 2009, 2017, MariaDB
+   Copyright (c) 2009, 2020, MariaDB
 
    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
@@ -3295,7 +3295,7 @@ CLI_MYSQL_REAL_CONNECT(MYSQL *mysql,const char *host, const char *user,
     /* New protocol with 16 bytes to describe server characteristics */
     mysql->server_language=end[2];
     mysql->server_status=uint2korr(end+3);
-    mysql->server_capabilities|= uint2korr(end+5) << 16;
+    mysql->server_capabilities|= ((unsigned) uint2korr(end+5)) << 16;
     pkt_scramble_len= end[7];
     if (pkt_scramble_len < 0)
     {