Dynamic dispatch for sparse matrices

[fabian-s]

Hi,

Dirk asked whether I wanted to write up an entry based on an answer I posted on StackOverflow, here it is: https://gist.github.com/fabian-s/9665846

Best wishes & thanks for the great work you all are doing with Rcpp,
Fabian

[eddelbuettel]

Super -- will look more closely this eve and commit. You've already won on my number one nag: people tend to invent new tags, and you refrained from that :)

[eddelbuettel]

And done -- nice post, I did one minor reindent, so thanks!