Replace cBind by cbind (#3203)

* modify test_helper.R

* fix noLD

* update desc

* fix solaris test

* fix desc

* improve fix

* fix url

* change Matrix cBind to cbind

* fix

* fix error in demo

* fix examples

R-package/R/xgboost.R

@@ -77,7 +77,6 @@ NULL
 
 # Various imports
 #' @importClassesFrom Matrix dgCMatrix dgeMatrix
-#' @importFrom Matrix cBind
 #' @importFrom Matrix colSums
 #' @importFrom Matrix sparse.model.matrix
 #' @importFrom Matrix sparseVector