WIP: Add missing requirements for random access iterators

In this patch, also add all the missing checks in existing algorithms
and add tests for those.
This can be done before the large refactoring

Author: ldionne

libcxx/test/support/test_iterators.h

@@ -1484,9 +1484,14 @@ class iterator_wrapper {
     return tmp;
   }
 
-  iterator_wrapper& operator+=(difference_type i) {
+  Derived& operator+=(difference_type i) {
     iter_ += i;
-    return *this;
+    return static_cast<Derived&>(*this);
+  }
+
+  Derived& operator-=(difference_type i) {
+    iter_ -= i;
+    return static_cast<Derived&>(*this);
   }
 
   friend decltype(iter_ - iter_) operator-(const iterator_wrapper& lhs, const iterator_wrapper& rhs) {
@@ -1503,8 +1508,17 @@ class iterator_wrapper {
     return iter;
   }
 
+  friend Derived operator+(difference_type i, Derived iter) {
+    return iter + i;
+  }
+
   friend bool operator==(const iterator_wrapper& lhs, const iterator_wrapper& rhs) { return lhs.iter_ == rhs.iter_; }
   friend bool operator!=(const iterator_wrapper& lhs, const iterator_wrapper& rhs) { return lhs.iter_ != rhs.iter_; }
+
+  friend bool operator>(const iterator_wrapper& lhs, const iterator_wrapper& rhs) { return lhs.iter_ > rhs.iter_; }
+  friend bool operator<(const iterator_wrapper& lhs, const iterator_wrapper& rhs) { return lhs.iter_ < rhs.iter_; }
+  friend bool operator<=(const iterator_wrapper& lhs, const iterator_wrapper& rhs) { return lhs.iter_ <= rhs.iter_; }
+  friend bool operator>=(const iterator_wrapper& lhs, const iterator_wrapper& rhs) { return lhs.iter_ >= rhs.iter_; }
 };
 
 class iterator_error : std::runtime_error {