- revert wrong include of zlib.h as zlib is not part of the source

   distribution - better use -I../zlib where appropriate (usually we use
   the zlib installed in the system)

sql/item_strfunc.cc

@@ -2572,7 +2572,7 @@ null:
 }
 
 #ifdef HAVE_COMPRESS
-#include "../zlib/zlib.h"
+#include "zlib.h"
 
 String *Item_func_compress::val_str(String *str)
 {