Update zlib to 1.2.5.

third_party/zlib/contrib/minizip/mztools.h

Index: third_party/zlib/contrib/minizip/mztools.h
===================================================================
--- third_party/zlib/contrib/minizip/mztools.h	(revision 113739)
+++ third_party/zlib/contrib/minizip/mztools.h	(working copy)
@@ -11,22 +11,24 @@
 extern "C" {
 #endif
 
+#ifndef _ZLIB_H
 #if defined(USE_SYSTEM_ZLIB)
 #include <zlib.h>
 #else
 #include "third_party/zlib/zlib.h"
 #endif
+#endif
 
 #include "unzip.h"
 
-/* Repair a ZIP file (missing central directory) 
+/* Repair a ZIP file (missing central directory)
    file: file to recover
    fileOut: output file after recovery
    fileOutTmp: temporary file name used for recovery
 */
-extern int ZEXPORT unzRepair(const char* file, 
-                             const char* fileOut, 
-                             const char* fileOutTmp, 
+extern int ZEXPORT unzRepair(const char* file,
+                             const char* fileOut,
+                             const char* fileOutTmp,
                              uLong* nRecovered,
                              uLong* bytesRecovered);