Rename crypt_msg() / decrypt_msg() to sed_encrypt_msg() / sed_decrypt_msg() and move to ctcp.c

These functions are really specific to parsing and creating CTCP SED messages, which means they belong
in ctcp.c with the other CTCP code.

Also remove unnecessary inclusions of encrypt.h and ctcp.h.

source/tcl.c

@@ -12,7 +12,6 @@
 #include "server.h"
 #include "chelp.h"
 #include "commands.h"
-#include "encrypt.h"
 #include "vars.h"
 #include "ircaux.h"
 #include "lastlog.h"