WL#3002: Make bind-address more flexible

Currently, the "bind-address" option just supports one IP address. Which means
that one can either instruct mysqld to listen on one IP address (by setting this
option) or on all available interfaces. It would be nice to be able to provide
multiple IP addresses via this variable, to have some more fine-grained control
on which interfaces mysqld is supposed to be listening on.

Duplicate of WL #621 ?
-- hartmut