Interface change: use R_xlen_t for loop unrolling

[krlmlr]

To compile RSQLite with -Wconversion -Werror.

[eddelbuettel]

Looks good to me. Anybody else see issues?

[krlmlr]

Thanks for reviewing. Is it important to update the copyright year in the files? I have missed a few instances (also in the other PR).

[eddelbuettel]

I do it when I remember it (which I usuallly do) but I am also not that religious about. You can add a commit, or we clean up another time...

[kevinushey]

LGTM, although I would (very marginally) prefer to see us selecting R_xlen_t vs. int depending on whether the input SEXPTYPE supports long vectors or not. Perhaps something for a separate PR some day?

[eddelbuettel]

Fair point. I guess a reverse depends check will give us some clues.

[eddelbuettel]

Passed a full reverse-depends check with flying colour, merging.