added notes to readme.txt about NumPy targets;
added some symbols to python_nt.def.

- Changed names of various things
- Explain how to recreate .exp files.

Under Windows, add MS_DLL_ID and MS_DLL_VERSION_ID for Mark H.

Independent change: if Py_TRACE_REFS is defined, rename Py_InitModule4
so so linking with incompatible modules will create a link time error.

[Backing out of previous changes (also for modsupport.c) to test
the latter at runtime.]

you do:
    imghdr.what(None, '')
And still go down the

- environment.c (we now have os.putenv)
- sybase (a better one is in contrib/Databases/Sybase.*)
- objc.c (incomplete and unsupportable by us)

try to do the mkdir whenever a new python has been built...

Renamed and, or to and_, or_.
Renamed all internal identifiers so as not to start with '__' (which is
a compiler privilege); remove AIX hack.