Track malloc size with a header for SHOW_MEMORY

HashTable.cpp

@@ -102,7 +102,7 @@ ConflictSet::ConflictSet(int64_t oldestVersion)
 ConflictSet::~ConflictSet() {
   if (impl) {
     impl->~Impl();
-    free(impl);
+    safe_free(impl);
   }
 }
 
@@ -142,6 +142,6 @@ ConflictSet_create(int64_t oldestVersion) {
 __attribute__((__visibility__("default"))) void ConflictSet_destroy(void *cs) {
   using Impl = ConflictSet::Impl;
   ((Impl *)cs)->~Impl();
-  free(cs);
+  safe_free(cs);
 }
 }