netkit-rsh: fix build issue.

glibc deprecate union wait and remove support from wait functions
https://sourceware.org/ml/libc-alpha/2016-02/msg00342.html


change rlogin.c accordingly

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>
(cherry picked from commit 62e3df2ddbeff9f2293027af6f159260cd2ab134)
Signed-off-by: Armin Kuster <akuster808@gmail.com>