(Redoing the checking without merging in Jack's buffer mods.)

All per-thread globals are moved into a struct which is manipulated
separately.

These are no longer needed as of FreeBSD 2.0.5, according to
Thomas Gellekum <tg@ihf.rwth-aachen.de>.

	was all that the method set anyway).  Removed calls to the
	constructor.  This reduces the number of Python function calls
	per widget construction by one, for every widget construction.

pystate.h (to be restored later when that code is debugged), removed
accessobject.h.

allobjects.h disappears -- old-style extensions must include Python.h
and rename2.h.

This requires Andrew Kuchling's zlib extension module.
It still needs some doc strings.

the value at configure time of the SGI_ABI environment variable.  See
abi(5).

when the pthread package is not installed.  configure knows better, so
#undef _POSIX_THREADS when pthread.h does not exist.

better than the old error API.