mysqld config: rename key_buffer -> key_buffer_size

Short name version is deprecated. Use full name instead.
https://mariadb.com/kb/en/mariadb/myisam-system-variables/#key_buffer_size

Author: ottok

debian/additions/mariadb.conf.d/server.cnf

@@ -31,7 +31,7 @@ bind-address		= 127.0.0.1
 #
 # * Fine Tuning
 #
-key_buffer		= 16M
+key_buffer_size		= 16M
 max_allowed_packet	= 16M
 thread_stack		= 192K
 thread_cache_size       = 8