Patch for Evo 2.30 - size of mail sidebar

[Federico Mena Quintero <federico novell com>]

Dear release team,

In Evolution 2.29, the mail sidebar (the tree of mail folders) starts up
with a ridiculously small width, so you can't read anything.  It's the
old pain of a treeview-in-an-hpaned.  So this patch sets up a reasonable
width.  We already have this in Evo master - OK to push to the
gnome-2-30 branch?

  Federico