While setlocale() is present, musl currently doesn't provide a suitable implementation.
It'll silently accept every locale, even if not present at all, defaulting them
to C.UTF-8. This will confuse applications as well as our testsuite(see lib/locale.t).

Even if a locale does exist, it's effects will not apply to an extent that will
satisfy many applications.

Avoid further mischief here and just disable setlocale() for now.

Signed-off-by: Marcel Denia <naoir@gmx.net>

This replaces the previously used collection of configuration files for every single
architecture in conjunction with hacky overrides, which became an increasing burden to maintain.

Fixes a number of outstanding bugs and oddities, with the most important one being the
previously wrong signal order(as shown by ext/POSIX/t/sigaction.t).

See files/perlconfig.pl's POD and files/README.config for details.

Signed-off-by: Marcel Denia <naoir@gmx.net>