Add a remove method to the hash map

src/hashmap.h

Index: src/hashmap.h
===================================================================
--- src/hashmap.h	(revision 1955)
+++ src/hashmap.h	(working copy)
@@ -75,6 +75,9 @@
   // Otherwise, NULL is returned.
   Entry* Lookup(void* key, uint32_t hash, bool insert);
 
+  // Removes the entry with matching key.
+  void Remove(void* key, uint32_t hash);
+
   // Empties the hash map (occupancy() == 0).
   void Clear();