A few more deprecated iterator fixes

std::iterator is deprecated in C++17

Author: eeckstein

lib/SILGen/SILGenApply.cpp

@@ -2251,9 +2251,13 @@ class ClaimedParamsRef {
     checkParams();
   }
 
-  struct iterator : public std::iterator<std::random_access_iterator_tag,
-                                         SILParameterInfo>
-  {
+  struct iterator {
+    using iterator_category = std::random_access_iterator_tag;
+    using value_type = SILParameterInfo;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type*;
+    using reference = value_type&;    
+
     const SILParameterInfo *Base;
     unsigned I, SkipParamIndex;
 

lib/SILOptimizer/PassManager/PassManager.cpp

@@ -1028,9 +1028,13 @@ namespace {
       SmallVector<Edge, 8> Children;
     };
 
-    struct child_iterator
-        : public std::iterator<std::random_access_iterator_tag, Node *,
-                               ptrdiff_t> {
+    struct child_iterator {
+      using iterator_category = std::random_access_iterator_tag;
+      using value_type = Node*;
+      using difference_type = std::ptrdiff_t;
+      using pointer = value_type*;
+      using reference = value_type&;    
+
       SmallVectorImpl<Edge>::iterator baseIter;
 
       child_iterator(SmallVectorImpl<Edge>::iterator baseIter) :