This patch adds missing headers in vendored zlib as done in numcodecs.js
diff --git a/c-blosc/internal-complibs/zlib-1.2.8/gzlib.c b/c-blosc/internal-complibs/zlib-1.2.8/gzlib.c
index fae202e..80606a6 100644
--- a/c-blosc/internal-complibs/zlib-1.2.8/gzlib.c
+++ b/c-blosc/internal-complibs/zlib-1.2.8/gzlib.c
@@ -2,7 +2,7 @@
  * Copyright (C) 2004, 2010, 2011, 2012, 2013 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
-
+#include <unistd.h>
 #include "gzguts.h"
 
 #if defined(_WIN32) && !defined(__BORLANDC__)

diff --git a/c-blosc/internal-complibs/zlib-1.2.8/gzread.c b/c-blosc/internal-complibs/zlib-1.2.8/gzread.c
index bf4538e..afe6acd 100644
--- a/c-blosc/internal-complibs/zlib-1.2.8/gzread.c
+++ b/c-blosc/internal-complibs/zlib-1.2.8/gzread.c
@@ -2,7 +2,7 @@
  * Copyright (C) 2004, 2005, 2010, 2011, 2012, 2013 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
-
+#include <unistd.h>
 #include "gzguts.h"
 
 /* Local functions */


diff --git a/c-blosc/internal-complibs/zlib-1.2.8/gzwrite.c b/c-blosc/internal-complibs/zlib-1.2.8/gzwrite.c
index aa767fb..a87676f 100644
--- a/c-blosc/internal-complibs/zlib-1.2.8/gzwrite.c
+++ b/c-blosc/internal-complibs/zlib-1.2.8/gzwrite.c
@@ -2,7 +2,7 @@
  * Copyright (C) 2004, 2005, 2010, 2011, 2012, 2013 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
-
+#include <unistd.h>
 #include "gzguts.h"
 
 /* Local functions */