Undo recent change that banned using import to bind a global, as per

discussion on python-dev.  'from mod import *' is still banned except
at the module level.

Fix value for special NOOPT entry in symtable.  Initialze to 0 instead
of None, so that later uses of PyInt_AS_LONG() are valid.  (Bug
reported by Donn Cave.)

replace local REPR macros with PyObject_REPR in object.h