* Use of TLS in pop3d and imap4d

If not explicitly specified, the TLS mode to use (ondemand, connect,
etc.) is derived from the configured port.  E.g., for imap4d, port 143
implies ondemand mode, and port 993 implies connection mode.

The global tls-mode setting is used only when the mode cannot be
detemined otherwise, i.e. neither per-server tls-mode is given nor
the port gives any clues as to the TLS mode to use.

* Bugfixes

** movemail: fix handling of -P option.
** pop3d, imap4d: fix global timeout and transcript configuration statements
** pop3d, imap4d: global tls-mode is used only when the mode to use cannot
   be determined otherwise.
** pop3d, imap4d: if not set explicitly, derive tls mode from the port used.
** Improve file safety checking routine.
** Fix compilation with new gcc versions.