check for __sync_add_and_fetch

configure.ac

@@ -476,6 +476,15 @@ AC_CHECK_FUNCS([				\
 	yp_get_default_domain			\
 ])
 
+AC_MSG_CHECKING([checking for __sync_add_and_fetch])
+AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <sys/types.h>]],
+	[[unsigned int foo; __sync_add_and_fetch(&foo, 1);]])],
+	[ac_rk_have___sync_add_and_fetch=yes], [ac_rk_have___sync_add_and_fetch=no])
+if test "$ac_rk_have___sync_add_and_fetch" = "yes" ; then
+	AC_DEFINE_UNQUOTED(HAVE___SYNC_ADD_AND_FETCH, 1, [have __sync_add_and_fetch])
+fi
+AC_MSG_RESULT($ac_rk_have___sync_add_and_fetch)
+
 AC_FUNC_MMAP
 
 KRB_CAPABILITIES