Basic filter implementation

[Emmanuel <e allaud wanadoo fr>]

	Hi all,
I've done all the basic implementation for filtering.
What it does :
-implements all filtering functions needed to filter messages (regular 
expression filters, and simple filters (just matching string that has to 
be [not] contained in header/body);
-implements the filters dialog;
-implements the save/load of filters via gnome_config.
What it does not do:
-No filter run dialog (to run filters manually on mailboxes);
-No notification on succes (sound, text popup...);
- more crucial : it lacks 2 important things where I deseperatly need 
helps :
  * first I just have made compilation tests because I can't run balsa 
on my box because of lack of recent libs, so the thing I lack is heavy 
testing for correctness and usability (I guess that there are 
GUI-problems, sure the layout is ugly...), so I need feedback.
  * second I've no idea how to plug the filtering function when balsa 
fetches mails, so if someone would be kind enough to take care of this : 
you only need the filtering function gint filter_run_all(GList * 
filter_list, LibBalsaMessage * message) which returns TRUE if one of the 
filters of filter_list has matched, and the balsa_app.filters member 
containing the list of filters.
I've tried my best to document sources, but I'm available to answer any 
questions (just be patient I'm not online all day :).
Patchs are ready against vanilla 1.1.7.
Thanks