Don't abbreviate Find Prev Selected.
Add ui_tree_view_find_previous().
Set Next Message menu item sensitivity when clicking on Search menu.
Thanks to Beau Barker (skip76) for an initial version of
ui_tree_view_find_previous() (see #1931125).


git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@2725 ea778897-0a13-0410-b9d1-a72fbfd435f5