Add NO_STL std::reverse implementation (#174)

Follows the example implementation on [1].

[1] https://en.cppreference.com/w/cpp/algorithm/reverse

include/etl/stl/alternate/algorithm.h

@@ -156,6 +156,17 @@ namespace ETLSTD
     return de;
   }
 
+  //***************************************************************************
+  // reverse
+  template<typename TIterator>
+  void reverse(TIterator first, TIterator last)
+  {
+    while ((first != last) && (first != --last))
+    {
+      ETLSTD::swap(*first++, *last);
+    }
+  }
+
   //***************************************************************************
   // move
   template <typename TIterator1, typename TIterator2>