check the existence of destination folder when editing filter rule.
made 'is shorter than' default for 'Age' condition on filter/search dialog.
added new plug-in signals for preferences dialogs (#30)
made the default boolean type of query search and filter condition AND.
removed warnings 'GtkSpinButton: setting an adjustment with non-zero page size is deprecated'.
src/prefs_filter_edit.c: modified menu string.
added a new filter match type: is (not) in addressbook.
added new search folder icon.
use target header field as a default filter name when creating filter rule automatically.
win32: made a workaround for the redraw problem in GTK+ 2.10.11.
fixed a memory leak. made 2.4.0beta3 release.
fixed saved search.
support Oniguruma for regex.
disabled regex match type on win32.
added filter conditions of status such as 'unread', 'mark', 'color-label', and 'mime'.
partially implemented search folder properties.
added a function for minor code cleanup.
implemented query search and virtual folder (merged from newsearch branch).
prefs_filter_edit_cond_hbox_to_cond(): added an argument for case sensitivity.
made more prefs_filter functions public.
prefs_filter_edit.c: generalized the condition edit.
made CondHBox / ActionHBox related APIs public.
fixed Turkish locale problem.
prefs_filter_edit.c: display unit on AGE condition.
replaced intl.h with glib/gi18n.h.
prefs_filter_edit.c: use GTK stock icon for add and remove button.
use GTK stock button for button set.
Initial import of Sylpheed (GTK2 version).