Fix a reference leak found by Georg, when compiling a class nested in another class.

Now "regrtest.py -R:: test_compile" is satisfied.

Will backport.

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 2.6 alpha 2?
 Core and builtins
 -----------------
 
+- The compilation of a class nested in another class used to leak one
+  reference on the outer class name.
+
 - Patch #1810: compile() can now compile _ast trees as returned by
   compile(..., PyCF_ONLY_AST).
 

Python/compile.c

@@ -1431,6 +1431,7 @@ compiler_class(struct compiler *c, stmt_ty s)
 	if (!compiler_enter_scope(c, s->v.ClassDef.name, (void *)s,
 				  s->lineno))
 		return 0;
+	Py_XDECREF(c->u->u_private);
 	c->u->u_private = s->v.ClassDef.name;
 	Py_INCREF(c->u->u_private);
 	str = PyString_InternFromString("__name__");