This fixes a number of things that are warnings in the Mac compiler....

import/cross/zip_archive.cc

 /*
  * Copyright 2009, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 845 matching lines @@
     if (tempfile) {
       fwrite(data, 1, data_size, tempfile);
       fclose(tempfile);
       *temp_filename = fullpath;
     } else {
       return false;
     }
 
 #else
     // get just the final path component
-    int pos = filename.rfind('/');
+    string::size_type pos = filename.rfind('/');
     if (pos != string::npos) {
       // TODO : need to get "proper" temp dir for user
       // TODO : need to append GUID to filename
       std::string tmp = "/tmp/" + filename.substr(pos + 1);
       FILE *fp = fopen(tmp.c_str(), "w");
 
       if (fp) {
         fwrite(data, 1, data_size, fp);
         fclose(fp);
         *temp_filename = tmp;
       } else {
         return false;
       }
     }
 #endif
   }
 
   return true;
 }
 
 void ZipArchive::DeleteFile(const string &filename) {
 #if defined(OS_WIN)
   ::_unlink(filename.c_str());
 #else
   ::unlink(filename.c_str());
 #endif
 }