Add check for kernel semaphore support and disable udev_sync if not available.
udev_sync feature requires semaphores (part of System V IPC) to be configured
in kernel (CONFIG_SYSVIPC). Check whether it is supported and if not, give
a warning message and disable udev synchronisation code automatically to
avoid any further error states and associated problems.
One should use the kernel with System V IPC support enabled or libdevmapper
with udev_sync feature disabled.