Do not use the non-standard <sys/cdefs.h> header

<sys/cdefs.h> is glibc-specific, and should be used only internally by
glibc, not by external libraries/programs. It is not available in all
standard C libraries.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
(Patch sent upstream: https://sourceforge.net/p/linknx/patches/21/)

diff -uNr linknx-0.0.1.32.org/include/eibclient.h linknx-0.0.1.32/include/eibclient.h
--- linknx-0.0.1.32.org/include/eibclient.h	2007-10-11 01:55:33.000000000 +0200
+++ linknx-0.0.1.32/include/eibclient.h	2016-01-23 23:21:17.315006629 +0100
@@ -27,11 +27,12 @@
 #ifndef EIBCLIENT_H
 #define EIBCLIENT_H
 
-#include "sys/cdefs.h"
 #include "stdint.h"
 #include <pthsem.h>
 
-__BEGIN_DECLS;
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 #include "eibloadresult.h"
 
@@ -705,5 +706,8 @@
  */
 int EIB_LoadImage_async (EIBConnection * con, const uint8_t * image, int len);
 
-__END_DECLS
+#ifdef __cplusplus
+}
+#endif
+
 #endif