ANN: Updating flag description in the User's Guide

[Jan Stolarek]

> Sometimes we add flags that are for experimentation or development
> purposes and not intended for user consumption, and these tend not to be
> added to the User's Guide.  I suspect many of the flags you mention fall
> into this category.  I suggest for these we have a specific comment in
> the source "developer use only; undocumented" so that we know they don't
> need to go in the User's Guide.
I don't like that policy. What if some of the mentioned flags could be useful for my development 
work but I have no idea how to use these flags because they are not documented? I think we should 
have these documented as well, possibly with a note saying that this is experimental/unstable.

> isn't -ddump-simpl-phases useful?  what's the other way to do that?
I'll reply in a thread started by Johan.

Janek