Defining a common plugin machinery

After the FSF gives final approval on the plugin feature, we will need
to coordinate towards one common plugin interface for GCC.  I don't 
think we should be adding two different and incompatible plugin harnesses.

I am CCing everyone who I know is working on plugin features.  Apologies 
if I missed anyone.

I would like to start by understanding what the plugin API should have. 
  What features do we want to support?  What should we export?  What 
should be the user interface to incorporate plugin code?  At what point 
in the compilation stage should it kick in?

Once we define a common API and then we can take the implementation from 
the existing branches.  Perhaps create a common branch?  I would also 
like to understand what the status and features of  the different 
branches is.

If it would help to have a conference call or IRC meeting, I can set one 
up for all the parties interested.  But first, I would like to hash the 
main issues on the lists.


Thanks.  Diego.