Allow control over how the encoding matrix is built

[hivenet-mathieu-lacage]

Allow users to pick an encoding matrix that is compatible with the klauspost/reedsolomon library.

The zfec library uses a vector of alpha^i to create its encoding matrix from the vandermonde matrix. From the original paper: https://www.cs.utexas.edu/users/lam/395t/papers/FEC-rizzo.pdf

Some libraries use another common convention where the encoding matrix is built from the vandermonde matrix from a vector of sequential integers (0, 1, 2, 3, ...). The objective of this patch is to allow zfec to generate and consume data using this convention.

[hivenet-mathieu-lacage]

Hi @exarkun , I see you have merged a couple of PRs over the project's recent history. Do you have any interest in this PR ? I do not mind taking time to rework this if the project is interested but if you are not, it would be nice to know :)

[exarkun]

Hi @exarkun , I see you have merged a couple of PRs over the project's recent history. Do you have any interest in this PR ? I do not mind taking time to rework this if the project is interested but if you are not, it would be nice to know :)

I'm not as active on this project any more but I may be able to take a look sometime (esp. after I return from a trip I'm currently on).

[hivenet-mathieu-lacage]

@exarkun if you are not able to have a look this, can you suggest anyone who might care enough to tell me if this makes any sense for you or if I need to move on and find an alternate solution ?