pROC 1.12.0 cannot deal with large datasets any longer

[xrobin]

Describe the bug
This is a regression due to the fix in #25

To Reproduce

> response <- rbinom(1E5, 1, .5)
> predictor <- rnorm(1E5)
> rocobj <- roc(response, predictor)
Erreur : impossible d'allouer un vecteur de taille 74.5 Go
4: outer(thresholds, predictor, `==`) at roc.utils.R#119
3: roc.utils.thresholds(c(controls, cases), direction) at roc.R#316
2: roc.default(response, predictor) at roc.R#21
1: roc(response, predictor)

This is caused by the check for identical values:

if (any(o <- outer(thresholds, predictor, `==`))) {

There must be an other way to test for exact equality between two vectors safely.

[xrobin]

Fixed on master. Will push pROC 1.12.1 to CRAN ASAP.