battery: Update AC status on FreeBSD

src/battery/freebsd.c

@@ -69,6 +69,9 @@ int battery_os_update(struct batstate *state) {
 	else
 		err = -1;
 
+	if (sysctlbyname("hw.acpi.acline", &sysctl_out, &len, NULL, 0) == 0)
+		state->ac_connected = sysctl_out;
+	
 	return err;
 }