String intern table and support for unordered_map

Change-Id: I22d86d060780552675c5d7f14a98ffde480eac82
diff --git a/src/zip_archive.cc b/src/zip_archive.cc
index 09dc3d4..a615321 100644
--- a/src/zip_archive.cc
+++ b/src/zip_archive.cc
@@ -310,7 +310,7 @@
 
 ZipEntry* ZipArchive::Find(const char* name) {
   DCHECK(name != NULL);
-  std::map<StringPiece, const uint8_t*>::const_iterator it = dir_entries_.find(name);
+  DirEntries::const_iterator it = dir_entries_.find(name);
   if (it == dir_entries_.end()) {
     return NULL;
   }