Polynomial Code for ISA-L erasure code - optional faster encode - decode unchanged

The intended ISA-L use case is as an erasure only code. Polynomial code could do a somewhat faster single thread full encode using LFSR, but would require separate software for LFSR based encoding. Multi-threading would be a simpler way to increase throughput, I don't have any plans to create a repository for LFSR based encoding unless there is some interest in this.

For erasure codes like ISA-L, error checking | correction would be normally be handled externally, such as the ZFS file system. If error checking | correction was to be added to erasure code, a polynomial code based matrix can be used for encoding.