File gnu-source.patch of Package libxls

diff -rupN libxls-new/src/xlstool.c libxls/src/xlstool.c
--- libxls-new/src/xlstool.c	2014-01-11 23:06:35.000000000 +0100
+++ libxls/src/xlstool.c	2017-10-27 18:14:25.321102192 +0200
@@ -30,6 +30,8 @@
  *
  */
 
+#define _GNU_SOURCE
+
 #include "config.h"
 
 #include <math.h>
@@ -48,6 +50,9 @@
 #include <memory.h>
 #include <string.h>
 
+#include <unistd.h>
+#include <sys/socket.h>
+
 //#include "xls.h"
 #include "libxls/xlstypes.h"
 #include "libxls/xlsstruct.h"