* posix/sys/wait.h [__WIFCONTINUED] (WIFCONTINUED): New macro.
* stdlib/stdlib.h [__WIFCONTINUED] (WIFCONTINUED): New macro.
* sysdeps/generic/bits/waitstatus.h (__W_CONTINUED): New macro.
[WCONTINUED] (__WIFCONTINUED): New macro.
(__WIFSIGNALED): Rewritten to exclude __W_CONTINUED value, and have no
branches.
* posix/tst-waitid.c (test_child): Sleep a second before stopping.
(do_test): Bump sleep to three seconds.
(sigchld, check_sigchld): New functions.
(do_test): Handle SIGCHLD and check for getting the right details.