implemented remote POP3 mailbox.
impelmented POP before SMTP.
exclude messages marked as read when counting new messages.
fixed 32-bit integer overflow where the total size of POP3 messages is greater than 2GB.
prevent duplicate retrieval after incomplete POP3 session.
changed the license of LibSylph from GPL to LGPL.
save GPG settings even if GPGME is disabled.
moved more modules to libsylph.
Initial import of Sylpheed (GTK2 version).