Bug #74429 system_time_zone generates warning if zone name contains non-ascii chars

Description:
Time zone setting on Windows non-English language may contain non-ASCII chars, e.g. "Mitteleuropäische Sommerzeit" on German translated Windows 7 Professional. When this happens 'system_time_zone' is truncated at the 1st non-ASCII char and consulting it generates a warning. Theoretically this can happen in other systems too.

This is particularly relevant for Connector/J since it consults this value on every new connection and the warning keeps showing up in the logs.

Although the "How To Repeat" shows an example ran on a MySQL 5.1.73, the same results were verified with the latest MySQL 5.7 sources, so the bug may exist in all current versions.

Related bugs:
- http://clustra.no.oracle.com/orabugs/19582659
- http://clustra.no.oracle.com/orabugs/11761893 (derived from the original report)

How to repeat:
Set the time zone to "Mitteleuropäische Sommerzeit" on a Windows 7 with German language pack.

Betriebssystemname
	Microsoft Windows 7 Professional
Version
	6.1.7601 Service Pack 1 Build 7601
(...)
Zeitzone
	Mitteleuropäische Sommerzeit

mysql> show variables like "%version%";
+-------------------------+------------------------------+
| Variable_name           | Value                        |
+-------------------------+------------------------------+
| protocol_version        | 10                           |
| version                 | 5.1.73-community             |
| version_comment         | MySQL Community Server (GPL) |
| version_compile_machine | unknown                      |
| version_compile_os      | Win64                        |
+-------------------------+------------------------------+
5 rows in set (0.00 sec)

mysql> show variables like "%char%";
+--------------------------+---------------------------------------------------------+
| Variable_name            | Value                                                   |
+--------------------------+---------------------------------------------------------+
| character_set_client     | utf8                                                    |
| character_set_connection | utf8                                                    |
| character_set_database   | latin1                                                  |
| character_set_filesystem | binary                                                  |
| character_set_results    | utf8                                                    |
| character_set_server     | utf8                                                    |
| character_set_system     | utf8                                                    |
| character_sets_dir       | C:\Program Files\MySQL\MySQL Server 5.1\share\charsets\ |
+--------------------------+---------------------------------------------------------+
8 rows in set (0.00 sec)

mysql> show variables like "%zone%";
+------------------+-------------+
| Variable_name    | Value       |
+------------------+-------------+
| system_time_zone | Mitteleurop |
| time_zone        | SYSTEM      |
+------------------+-------------+
2 rows in set, 1 warning (0.01 sec)

mysql> show warnings;
+---------+------+-----------------------------------------------------------------------------+
| Level   | Code | Message                                                                     |
+---------+------+-----------------------------------------------------------------------------+
| Warning | 1366 | Incorrect string value: '\xE4ische...' for column 'VARIABLE_VALUE' at row 1 |
+---------+------+-----------------------------------------------------------------------------+
1 row in set (0.00 sec)

Suggested fix:
-

This is still occurring with mysql 5.7.11
Our computers are installed with windows 7 french

show variables;
SHOW WARNINGS LIMIT 5; 
Warning	1366	Incorrect string value: '\x92\xE9t\xE9)' for column 'VARIABLE_VALUE' at row 478

row 478 is system_time_zone