XenForo Adding FAwesome icon in login/register button's

[CR LEAKS]

In extra.less:

.p-nav-opposite {
    .p-navgroup-link:before {
        padding-right: 5px;
        .m-faBase();
    }

    // Login
    .p-navgroup-link--logIn:before {
        .m-faContent(@fa-var-sign-in, .85em);
    }

    // Register
    .p-navgroup-link--register:before {
        .m-faContent(@fa-var-unlock-alt, .85em);
    }
}