htl: move __pthtread_total into libc

htl/pt-nthreads.c: new file.
htl/Makefile: Add it to routine.
htl/Versions: version it as private libc symbol.
htl/pt-create.c: remove his definition here.
htl/pt-internal.h: add propertie to it declaration.

Signed-off-by: Guy-Fleury Iteriteka <gfleury@disroot.org>
Message-Id: <20230318095826.1125734-2-gfleury@disroot.org>