Builds without udev support

When the udev daemon isn't available in the system, the ReportKernelEvent method in the Manager interface may be used to notify the ModemManager daemons of device addition and removals.

When udev support is disabled in the build, the ID_MM_CANDIDATE tag and manual scan requests are still applicable. ModemManager has a built-in parser of udev rule files that is enabled when udev itself isn't available.