Fix build problems when using HashMap.

public/amtl/am-hashmap.h

@@ -57,6 +57,10 @@ class HashMap : public AllocPolicy
     K key;
     V value;
 
+    Entry()
+    {
+    }
+
     Entry(const K &aKey, const V &aValue)
      : key(aKey),
        value(aValue)
@@ -120,6 +124,13 @@ class HashMap : public AllocPolicy
     return table_.add(i, Entry(key, value));
   }
 
+  // This can be used to avoid compiler constructed temporaries, since AMTL
+  // does not yet support move semantics. If you use this, the key and value
+  // must be set after.
+  bool add(Insert &i) {
+    return table_.add(i);
+  }
+
   size_t estimateMemoryUse() const {
     return table_.estimateMemoryUse();
   }