* src/folder.[ch]
o add notification hook for folder tree changes
o invoke hooks after folder tree scanning
* src/folderview.[ch]
register hook for folder tree changes that
updates the ctree
(there are more places that should be updated, like add, remove
or move folder)
(closes Bug 164 Crash on rebuild folder tree)
(closes Bug 190 Crash on 'rebuilding folder tree')
added Makefile
* src/filtering.[ch]
* src/folder.[ch]
* src/folderview.[ch]
* src/import.c
* src/inc.[ch]
* src/mbox.[ch]
* src/procmsg.c
* src/summaryview.[ch]
o added new flag need_update to FolderItem
o removed folder_table from various functions from tracking
folder updates
o set need_update flags in folder.c's move, copy and delete
functions and procmsg's flags functions
o added function folderview_update_items_when_required that
updates all folders with need_update set
o call folderview_update_items_when_required instead of
folderview_update_item_foreach