fix #1969

[slingamn]

On a 32-bit architecture, 64-bit atomic loads and stores must be aligned to a
64-bit boundary. Since the (mysql.MySQL) struct is directly included in the
Server struct, it is impossible to guarantee this via the standard technique
of putting the 64-bit value at the beginning of the struct definition
(since the point at which it is included in the parent struct may cross a
64-bit boundary).

This optimization is probably pointless anyway, adding an additional
indirection won't make a difference.