[R] make all customizations to meet strict standard of cran

R-package/src/xgboost_R.cc

@@ -34,16 +34,6 @@
     error(XGBGetLastError());                   \
   }
 
-namespace xgboost {
-namespace common {
-bool CheckNAN(double v) {
-  return ISNAN(v);
-}
-double LogGamma(double v) {
-  return lgammafn(v);
-}
-}  // namespace common
-}  // namespace xgboost
 
 using namespace dmlc;