And performance tweaking for as()

Author: dcdillon

inst/include/Rcpp/Nullable.h

@@ -119,7 +119,7 @@ namespace Rcpp {
         /**
          * Returns m_sexp as a T
          */
-        inline T as() { return Rcpp::as< T >(get()); }
+        inline T as() { return get(); }
 
         /**
          * Return a clone of m_sexp as a T