(1) Use PyErr_NewException("module.class", NULL, NULL) to create the
    exception object.

(2) Remove all calls to Py_FatalError(); instead, return or
    ignore the errors -- the import code now checks PyErr_Occurred()
    after calling a module's init function, so it's no longer a
    fatal error for the initialization to fail.

Also did some small cleanups, e.g. removed unnecessary test for
"already initialized" from initfpectl(), and unified
initposix()/initnt().

I haven't checked this very thoroughly, so while the changes are
pretty trivial -- beware of untested code!

Since it only returns an error message (or NULL) there's no reason
for it to be unsigned char *, and various compilers like this better.

different in a future version.

otherwise laudible attempt to rationalize the argument parsing): it
would save a copy of the original string instead of a reference to it.
Go back to saving a reference, but keep the "s#" format (using a hack
that involves two argument parsing steps, first using "O", then using
"s#").

- Where optional arguments were being used, converted to
  PyArg_ParseTuple() style instead of nested PyArg_Parse() style.

- Check for and handle many potential error conditions that were never
  being tested.

- internal reg_* functions renamed to regobj_* (makes it easier to
  figure out which are global regex functions and which are for regex
  objects).

- reg_group (now regobj_group) was quite extensively reworked.  it no
  longer recurses to do its job (by factoring core functionality into
  a separate function that knows about string and integer indexes).

- some minor formatting fixes.

- regex_set_syntax() now invalidates the cache.  Without this change
  (in the example below), the second search would produce different
  output depending on whether the first search were performed or not
  (since performing the first search would cache the compiled object
  with RE_SYNTAX_EMACS, causing the second test to unexpectedly fail).

  regex.search('(a+)|(b+)', 'cdb')
  prev = regex.set_syntax(RE_SYNTAX_AWK)
  regex.search('(a+)|(b+)', 'cdb')

Thanks to Ka-Ping Yee.

Setup.in: clarified Tk comments somewhat.
structmodule.c: use memcpy() instead of double precision assignment.

Use getargs() function.
Drop re_string from re object.

GNU regular expressions