Common Library

* crc16.h and crc16.c were copied from the linux kernel.
* crc32.h and crc32.c were copied from mtd-utils and amended.
* defs.h is a bunch of definitions to smooth things over.
* hashtable/* was downloaded from http://www.cl.cam.ac.uk/~cwc22/hashtable/
* atomic.h was downloaded from https://the-linux-channel.the-toffee-project.org/index.php?page=6-tutorials-linux-user-space-atomic-operations
* bitops.h and bitops.c were copied from the linux kernel.
* compiler_attributes.h was copied from the linux kernel.
* linux_types.h was copied from the linux kernel.
* linux_err.h was copied from the linux kernel.
* hexdump.c was copied from the linux kernel.
* kmem.h and kmem.c were partial copied from xfsprogs-dev (https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/)
* sort.h and sort.c were copied from the linux kernel.