signup link always shows on adminbar in MU/network environment

[wpmuguru]

Sorry this isn't a patch file. The adminbar code expects bp_get_signup_allowed to return a true or false. It actually returns a false of the registration setting (none, all, etc.). This code returns the appropriate true/false:

	function bp_get_signup_allowed() {
		if ( bp_core_is_multisite() ) {
			if ( in_array( get_site_option( 'registration' ), array( 'all', 'user' ) ) )
				return true;
		} else {
			if ( (int)get_option( 'users_can_register') )
				return true;
		}
		return false;
	}

[wpmuguru]

forgot the has-patch

[apeatling]

(In [2492]) Fixes #1736 props wpmuguru