internally keep multiple applications of the same markers as separate

entities such that the new iter() API can iterate over pytest.mark
function attributes, getting all such applications.  See added example
for more info.

_pytest/mark.py

@@ -191,8 +191,7 @@ class MarkDecorator:
                         holder = MarkInfo(self.markname, self.args, self.kwargs)
                         setattr(func, self.markname, holder)
                     else:
-                        holder.kwargs.update(self.kwargs)
-                        holder.args += self.args
+                        holder.add(self.args, self.kwargs)
                 return func
         kw = self.kwargs.copy()
         kw.update(kwargs)
@@ -208,11 +207,23 @@ class MarkInfo:
         self.args = args
         #: keyword argument dictionary, empty if nothing specified
         self.kwargs = kwargs
+        self._arglist = [(args, kwargs.copy())]
 
     def __repr__(self):
         return "<MarkInfo %r args=%r kwargs=%r>" % (
                 self.name, self.args, self.kwargs)
 
+    def add(self, args, kwargs):
+        """ add a MarkInfo with the given args and kwargs. """
+        self._arglist.append((args, kwargs))
+        self.args += args
+        self.kwargs.update(kwargs)
+
+    def __iter__(self):
+        """ yield MarkInfo objects each relating to a marking-call. """
+        for args, kwargs in self._arglist:
+            yield MarkInfo(self.name, args, kwargs)
+
 def pytest_itemcollected(item):
     if not isinstance(item, pytest.Function):
         return