Persistent Memory block array support library

 libpmemblk implements a pmem-resident array of blocks, all the same size, where
 a block is updated atomically with respect to power failure or program
 interruption (no torn blocks).
 .
 This library is provided for cases requiring large arrays of objects at least
 512 bytes each. Most developers will find higher level libraries like
 libpmemobj to be more generally useful.