Fixes for upper_tri and lower_tri with unit tests (closes #641)

[nathan-russell]

With these changes,

#include <Rcpp.h>
using namespace Rcpp;

// [[Rcpp::export]]
LogicalMatrix UpperTri(NumericMatrix x, bool diag = false) {
    return upper_tri(x, diag);
}

// [[Rcpp::export]]
LogicalMatrix LowerTri(NumericMatrix x, bool diag = false) {
    return lower_tri(x, diag);
}

/*** R

x <- matrix(1:4, 4, 5)

all.equal(UpperTri(x), upper.tri(x))
# [1] TRUE

all.equal(UpperTri(x, TRUE), upper.tri(x, TRUE))
# [1] TRUE

all.equal(LowerTri(x), lower.tri(x))
# [1] TRUE

all.equal(LowerTri(x, TRUE), lower.tri(x, TRUE))
# [1] TRUE

*/

[eddelbuettel]

Looks good to me at a first glance.

[eddelbuettel]

Thanks for catching that here. Slowly changing them myself whenever I see one in a file I use.

[eddelbuettel]

I think one usually separates the years, so that would be 2010 - 2016 if the next one 2017 - ... No biggie.