Accomodate upcoming change in package Matrix (fixes #415)

[jaganmn]

Finally got around to working on this. A few comments:

• Perhaps verify that I haven't introduced whitespace issues. I noticed that my Emacs inserted tabs where the file otherwise had none. Well, I fixed whatever I saw ...
• Unrelated to the issue, I replaced 5 lines of code repeated throughout the file with a macro. It was too upsetting ...
• I noticed that in several places you have ncol + 1, where ncol is an int. Note that ncol may take the value INT_MAX and in that case ncol + 1 will overflow. The patch does not attempt to address this.
• I've used R_alloc somewhere, but maybe that is not idiomatic ... I needed to do a[i]++ and did not feel like checking whether that was legal for a of type IntegerVector rather than int * ...

[eddelbuettel]

Thanks for the follow-up! I had getting back to you on the TODO list has I was left a little bewildered and lost about what you wanted me to do. Will peruse the PR -- thanks for sending it in!