Add .size method to Row and Column inner classes

Author: vspinu

inst/include/RcppParallel/RMatrix.h

@@ -129,7 +129,11 @@ class RMatrix {
       inline size_t length() const {
          return parent_.ncol();
       }
-      
+
+      inline size_t size() const {
+        return parent_.ncol();
+      }
+
       inline T& operator[](std::size_t i) {
         return start_[i * parent_.nrow()];
       }
@@ -174,6 +178,7 @@ class RMatrix {
       inline const_iterator end() const { return end_; }
 
       inline size_t length() const { return end_ - begin_; }
+      inline size_t size() const { return end_ - begin_; }
 
       inline T& operator[](std::size_t i) {
         return *(begin_ + i);