Add meshlink_add_invitation_address(), deprecate meshlink_add_address().

Add meshlink_add_invitation_address(), deprecate meshlink_add_address().

This adds a function to add one or more application-controlled address and
port combinations to invitation URLs. It is meant to replace
meshlink_add_address(), which is too limited because it only allows one
address to be set, and doesn't allow a different port number to be set.