Missing minibuffer messages (was: obsoleting stuff)

[Stefan Monnier]

One of the problems with my Fload patch is that the message
telling users that a package is obsolete might be missed because
it might be immediately overwritten by something else.

One option is to add a (sit-for 2) right after the call to Fmessage,
but I was wondering whether there shouldn't be a better option:

1 - Mark some messages "important" which means "display them for at
    least X seconds".  I.e. when displayed, those messages are tagged
    with a timeout that says when they can be taken off.

2 - when trying to show another message, if there's an important
    message on display, just stuff the new message in a "queue of pending
    messages" that will be processed when the timeout triggers.

3 - when the minibuffer is requested and the echo area is busy with an
    important message, I'm not sure what we should do: maybe just wait
    with a sit-for, or maybe put the important message back on the message
    queue to be shown again afterwards.

Obviously, this is overkill if it's just for the `obsolete' message,
but I feel like it could be useful in more cases.


        Stefan