_dl_stack_used/user/etc. vs _dl_pthread_num_threads etc. is really an
nptl vs htl question rather than pthread being in libc.

This is not needed yet for htl (only the Linux mq_notify), but we can as
well just simplify the header.

thrd_{create,detach,exit,join}.
mtx_{init,destroy,lock,trylock,unlock,timeelock}.
cnd_{broadcast,destroy,init,signal,timewait,wait,destroy}
tss_{create,delete,get,set}. call_once.
Message-ID: <20251121191336.1224485-1-gfleury@disroot.org>

The benchtests does not define _LIBC.

Some kernels returns EINVAL for ioctl (PIDFD_GET_INFO) on pidfd
descriptors.

Checked on aarch64-linux-gnu with Linux 6.12.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

The compiler might not constant fold the call, which issues
linker error.

Reviewed-by: Sam James <sam@gentoo.org>

clangs warns of the implicit cast of RAND_MAX to float:

  error: implicit conversion from 'int' to 'float' changes value from
  2147483647 to 2147483648 [-Werror,-Wimplicit-const-int-float-conversion]

So make it explicit.

Reviewed-by: Sam James <sam@gentoo.org>

Similar to tst-printf-bz18872.sh, add the attribute_optimize to avoid
build failures with compilers that do not support "GCC optimize" pragma.

Reviewed-by: Sam James <sam@gentoo.org>

The f128 is not a valid floating constant suffix on clang.

Reviewed-by: Sam James <sam@gentoo.org>