Relax the rules for using 'from ... import *' and exec in the presence

of nested functions.  Either is allowed in a function if it contains
no defs or lambdas or the defs and lambdas it contains have no free
variables.  If a function is itself nested and has free variables,
either is illegal.

Revise the symtable to use a PySymtableEntryObject, which holds all
the revelent information for a scope, rather than using a bunch of
st_cur_XXX pointers in the symtable struct.  The changes simplify the
internal management of the current symtable scope and of the stack.

Added new C source file: Python/symtable.c.  (Does the Windows build
process need to be updated?)

As part of these changes, the initial _symtable module interface
introduced in 2.1a2 is replaced.  A dictionary of
PySymtableEntryObjects are returned.

Modules/symtablemodule.c

@@ -31,7 +31,7 @@ symtable_symtable(PyObject *self, PyObject *args)
 	st = Py_SymtableString(str, filename, start);
 	if (st == NULL)
 		return NULL;
-	t = Py_BuildValue("OO", st->st_symbols, st->st_scopes);
+	t = Py_BuildValue("O", st->st_symbols);
 	PySymtable_Free(st);
 	return t;
 }