webmin/virtualmin uses deprecated options for MySQL

When selecting MySQL "size" (small, medium, large or huge) during installation, some presets are stored in MySQL's global configuration file /etc/mysql/my.cnf

One of these options is key_buffer, which should be replaced by key_buffer_size, because it is deprecated and will be removed in a future release of MySQL.

Presets are stored in function sub list_mysql_size_settings { ... } in file /usr/share/webmin/virtual-server/feature-mysql.pl

Not sure about the following variable in file /usr/share/webmin/mysql/mysql-lib.pl:

@mysql_set_variables = ( "key_buffer", "sort_buffer", "net_buffer_length","myisam_sort_buffer_size" );