Added support for newer zlib with cleaned up namespace.

Author: Jacob Shaffer

Sources/unzip/ioapi.h

@@ -9,6 +9,11 @@
 #ifndef _ZLIBIOAPI_H
 #define _ZLIBIOAPI_H
 
+/* Gentoo removed OF from their copy of zconf.h (https://bugs.gentoo.org/show_bug.cgi?id=383179) */
+/* but our copy of minizip needs it. */
+#ifndef OF
+#define OF(args) args
+#endif
 
 #define ZLIB_FILEFUNC_SEEK_CUR (1)
 #define ZLIB_FILEFUNC_SEEK_END (2)