entirely redone operator overloading. The rules for class
instances are now much more relaxed than for other built-in types
(whose coerce must still return two objects of the same type)
* Objects/floatobject.c: add overflow check when converting float
to int and implement truncation towards zero using ceil/float
* Objects/longobject.c: change ValueError to OverflowError when
converting to int
* Objects/rangeobject.c: modernized
* Objects/stringobject.c: use HAVE_LIMITS instead of __STDC__
* Objects/xxobject.c: changed to use new style (not finished?)
03093a248d