support Oniguruma for regex.
added filter conditions of status such as 'unread', 'mark', 'color-label', and 'mime'.
some modification of searching.
implemented query search and virtual folder (merged from newsearch branch).
added utility functions for optimization of filter.
fixed execution failure on filtering if a file path includes space.
changed the license of LibSylph from GPL to LGPL.
moved more modules to libsylph.
moved procmsg.c::procmsg_get_filter_keyword() to filter.c::filter_get_keyword_from_msg().
moved two functions from prefs_filter.c to filter.c.
moved prefs_filter_read_config() to filter.c.
separated UI code from prefs.c.
check for regex.h and regcomp().
modify filter rules after moving folders.
fixed a bug in syncing folder path.
integrated junk filter setting into common prefs.
fixed Turkish locale problem.
replaced intl.h with glib/gi18n.h.
Initial import of Sylpheed (GTK2 version).