[patch] New validation output presentation

Hi,

	I wrote some new code to replace the old message box which simply
listed error messages in a window which could easily become too big. 
	The new validation output window included in this patch presents the
messages in a GtkTreeView with automatic scroll bars, has a Refresh
button, prints the current validation status, and if you click on an
error message the XML node associated with it is selected.
	It looks like that :
http://happypeng.free.fr/screenshots/mlview-validation.png

	We have switched to GNU arch, so I have an archive here : 
http://korydwenn.homelinux.org/~happypeng/mlview
	The patch is mlview--happypeng--0.7--patch-4 ; the branch was merged
with mlview--mainline--0.7--patch-6 so it is currently up to date and it
should work directly.

	GNU arch really *rocks*. :-) 

	Thanks to Strider who offered my space to put my archive online. I used
to use Free.fr (as Dodji did) and now it *sucks* (write-only FTP). We
may put code on GNA.org some day too. 

Cheers,

Nicolas Centa
"HappyPeng"