Move mutex, condvar, and thread-specific data routes, pthread_once, and
pthread_exit from libpthread to libc, along with low-level bits to
support them. Major bump to both libc and libpthread.

Requested by libressl team. Ports testing by naddy@
ok kettenis@

cleanup and consolidate the spinlock_lock (what a name!) code.
it's now atomic_lock to better reflect its usage, and librthread now
features a new spinlock that's really a ticket lock.
thrlseep can handle both types of lock via a flag in the clock arg.
(temp back compat hack)
remove some old stuff that's accumulated along the way and no longer used.
some feedback from dlg, who is concerned with all things ticket lock.
(you need to boot a new kernel before installing librthread)

The "powerpc" port which has supported the newer Apple Macintosh powerpc based
is being renamed to macppc. This is to allow sharing of common code
between different powerpc base platforms.

Most of the work involved in the renaming process was performed by miod@

Files moved from powerpc/include to macppc/include
Some files were not "moved" but wrapper files were created which include
the powerpc/include version.

Several of the powerpc/include files where changed to reflect that they
are POWERPC_* not MACHINE_*.

branches: 1.1.6;
move spinlock.h into the real world