least as big as a long. I believe this to be a safe assumption that is being
made in many parts of CPython, but a check could be added.

len(xrange(sys.maxint)) works now, so fix the testsuite's odd exception for
64-bit platforms too. It also fixes 'zip(xrange(sys.maxint), it)' as a
portable-ish (if expensive) alternative to enumerate(it); since zip() now
calls len(), this was breaking on (real) 64-bit platforms. No additional
test was added for that behaviour.

rangeobject.c has an #ifdef that is reached only when LONG_MAX != INT_MAX

Added XXX comment about why the undocumented PyRange_New() API function
is too broken to be worth the considerable pain of repairing.

Changed range_new() to stop using PyRange_New().  This fixes a variety
of bogus errors.  Nothing in the core uses PyRange_New() now.

Documented that xrange() is intended to be simple and fast, and that
CPython restricts its arguments, and length of its result sequence, to
native C longs.

Added some tests that failed before the patch, and repaired a test that
relied on a bogus OverflowError getting raised.