Move all handling of SED messages and notices into ctcp.c, re-enable SED notices

Actual encryped messages and notices are now printed directly from do_sed() / do_reply_sed().
Inline CTCP replacement is only done if the message cannot be decrypted (for the [ENCRYPTED MESSAGE]
placeholder).

This removes the need for the global flag 'sed' to alter the NOTICE and PRIVMSG handling.

A side-effect of this is that SED PRIVMSGs now do not go through the usual PRIVMSG ignore
and flood handling.  This is acceptable because messages can only go through this path if
the sender has actually been added as a SED peer with /ENCRYPT, and it still goes through
the CTCP ignore and flood handling.

Changelog

@@ -1,5 +1,8 @@
 [Changes 1.2.2]
 
+* Move all handling of SED messages and notices into ctcp.c, re-enable
+  SED notices. (caf)
+
 * Handle SED-encrypted CTCP replies properly. (caf)
 
 * Add sent_nick flag to NickList struct, bump MODULE_VERSION. (caf)