partner-contact/base_partner_merge/security/security.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record model="res.groups" id="group_partner_merge">
            <field name="name">Partner Merge</field>
        </record>
        <record model="res.groups" id="base.group_system">
            <field name="implied_ids" eval="[(4, ref('group_partner_merge'))]"/>
        </record>
    </data>
</openerp>