Bug #28832 SET character_set_client = ucs2 is exected, but server doesn't parse UCS2

Description:
The SQL parser is not capable of parsing any UCS2 strings, but allows the client to request it with

> SET character_set_client = ucs2;

How to repeat:
In 5.0+ UCS2 as result is supported:

> SET character_set_results = ucs2;
> SELECT @@character_set_results;
|  u c s 2                    |

(\0u\0c\0s\0002)

> SET character_set_client = ucs2;
> \0S\0E\0L\0E\0C\0T\0 \0001

fails with:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near \'\' at line 1

> SELECT 1

fails with:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near \'SELECT 1\' at line 1

... this is the wrong byte-stream for the charset, but it shows that somewhere internally something is expecting UCS2 now.

Test-Code:

#include <stdio.h>
#include <mysql.h>

#define C(x) x, sizeof(x) - 1

int exec_select(MYSQL *mysql, const char *q, size_t q_len) {
        MYSQL_RES *res;

        if (mysql_real_query(mysql, q, q_len)) {
               fprintf(stderr, "%s.%d: mysql_real_query(%s) failed: %s",
                                __FILE__, __LINE__,
                                "",
                                mysql_error(mysql));
               return 0;
        }

        if (NULL != (res = mysql_store_result(mysql))) {
                mysql_free_result(res);
        }

        return 0;
}

int main() {
        MYSQL *mysql;

        mysql = mysql_init(NULL);

        if (!mysql_real_connect(mysql, "127.0.0.1", "root", "", "", 3306, NULL, 0)) {
                fprintf(stderr, "%s.%d: mysql_real_connect() failed: %s", __FILE__, __LINE__, mysql_error(mysql));
                return -1;
        }

#if 0
        exec_select(mysql, C("SET character_set_results = ucs2"));
        exec_select(mysql, C("SELECT @@character_set_results"));
#else
        exec_select(mysql, C("SET character_set_client = ucs2"));
        exec_select(mysql, C("\0S" "\0E" "\0L" "\0E" "\0C" "\0T" "\0 " "\0""1"));
        exec_select(mysql, C("SELECT 1"));
#endif

        mysql_close(mysql);

        return 0;
}

Suggested fix:
return an error for:

SET character_set_client = ucs2;

Thank you for the report.

Verified as described.

See bug #31615: crash after set names ucs2 collate xxx