Use generated shim headers for zlib.

third_party/zlib/contrib/minizip/unzip.c

 /* unzip.c -- IO for uncompress .zip files using zlib
    Version 1.1, February 14h, 2010
    part of the MiniZip project - ( http://www.winimage.com/zLibDll/minizip.html )
 
          Copyright (C) 1998-2010 Gilles Vollant (minizip) ( http://www.winimage.com/zLibDll/minizip.html )
 
          Modifications of Unzip for Zip64
          Copyright (C) 2007-2008 Even Rouault
 
          Modifications for Zip64 support on both zip and unzip
@@ skipping 54 matching lines @@
 
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #ifndef NOUNCRYPT
         #define NOUNCRYPT
 #endif
 
-#if defined(USE_SYSTEM_ZLIB)
-#include <zlib.h>
-#else
 #include "third_party/zlib/zlib.h"
-#endif
 #include "unzip.h"
 
 #ifdef STDC
 #  include <stddef.h>
 #  include <string.h>
 #  include <stdlib.h>
 #endif
 #ifdef NO_ERRNO_H
     extern int errno;
 #else
@@ skipping 2030 matching lines @@
                                               &s->cur_file_info_internal,
                                               NULL,0,NULL,0,NULL,0);
     s->current_file_ok = (err == UNZ_OK);
     return err;
 }
 
 extern int ZEXPORT unzSetOffset (unzFile file, uLong pos)
 {
     return unzSetOffset64(file,pos);
 }