[finishing fix from earlier checkins]

Call set_lineno() in visitDiscard(), which will generate linenos for
discard statements, e.g. the statement "1/0"

Fixes SF bug #409587

Lib/compiler/pycodegen.py

@@ -495,6 +495,7 @@ class CodeGenerator:
     # misc
 
     def visitDiscard(self, node):
+        self.set_lineno(node)
         self.visit(node.expr)
         self.emit('POP_TOP')