Run-time NPTL detection

[Vincent Béron]

This is a first patch to let Wine run on either an NPTL enabled or not
system.

The remaining issues deal with linking ntdll to libpthread, and
autodetection in configure.

It's not production-ready yet, I'm aware that there are a couple rough
edges (ie, nptl_check passing from libwine to ntdll,
wine_pthread_init_(process,thread)_no_nptl, what really happens if run
on a system without NPTL).

It's been tested on RH9 with NPTL.

Comments?
Vincent