This is the same bug as bug 12165, but for readdir_r.  The
regression test covers both bug 12165 and bug 32126.

Reviewed-by: DJ Delorie <dj@redhat.com>

It verifies that rewinddir allows restarting the directory
iteration.

Reviewed-by: DJ Delorie <dj@redhat.com>

It tests long names and ENAMETOOLONG handling, specifically
for readdir_r.  This is a regression test for bug 14699,
bug 32124, and bug 32128.

Reviewed-by: DJ Delorie <dj@redhat.com>

It verfies that closedir deallocates memory and closes
file descriptors.

Reviewed-by: DJ Delorie <dj@redhat.com>

Reflow and sort Makefile.

Code generation changes present due to link order changes.

No regressions on x86_64 and i686.

clang emits an warning when a double alias redirection is used, to warn
the the original symbol will be used even when weak definition is
overridden.  However, this is a common pattern for weak_alias, where
multiple alias are set to same symbol.

Reviewed-by: Fangrui Song <maskray@google.com>

I used these shell commands:

../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")

and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.

I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah.  I don't
know why I run into these diagnostics whereas others evidently do not.

remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines