better error message for unicode coercion failure

seqlen==1 clause, before returning item, we need to DECREF seq.  In
the res=PyString... failure clause, we need to goto finally to also
decref seq (and the DECREF of res in finally is changed to a
XDECREF).  Also, we need to DECREF seq just before the
PyUnicode_Join() return.

1. PySequence_Fast_GET_ITEM is a macro and borrows a reference
2. The seq returned from PySequence_Fast must be decref'd

about int size mismatches at two calls to s_rand.  Stuffed in
casts to make the code do what it did before but w/o warnings --
although unclear that's correct!

implementation -- use PySequence_Fast interface to iterate over elements
interface -- if instance object reports wrong length, ignore it;
   previous version raised an IndexError if reported length was too high

-- added a few extra comments to locale.py

  value is calculated from the character values, in a way
  that makes sure an 8-bit ASCII string and a unicode string
  with the same contents get the same hash value.

  (as a side effect, this also works for ISO Latin 1 strings).

  for more details, see the python-dev discussion.

a representation of the configuration state in .ini format that can be read
back in by a future read() call.  Thus this class is now a back end
for .ini editors as well as parsers.

This patch is complete and tested, but exposes a bug in the ConfigParser
implementation which I have not yet fixed.  Because case information is
discarded during parsing, the output of write() has its case smashed.

I wrote this for a SourceForge interface script called forgetool.
Documentation for the new entry points included.

test_string and test_userstring run same tests for string methods

have already been checked in)

UNTESTED!

   for #100836, but implemented in a different way)

to match addition to test_unicode.py.

  There is a silly bug in the fall-back dumbdbm.py database package in
  the Python 1.5.2 standard distro. This bug causes any changes to an
  existing item to generate a new key, even when the key already
  exists.  After many updates, the .dir file used by dumbdbm grows to
  a huge size, and can cause filesystem problems.

added excplicit node * parameter to termvalid argument in
validate_two_chain_ops of parsermodule.c (as proposed by fred)