Revised TOP FIle Naming Schemes

All temporary .TOP files are being renamed to .TCH so there is less confusion
over which files can be deleted, and so the temporary files can be found
easier.  "TCH" stands for "TOP Chat", thus "TCH File" means "TOP Chat File"
which is pretty much accurate.

The following files have undergone naming structure changes.  The 5 chars for a
node space allows up to 32767 nodes to be safely used.

    MIDX###.TOP ---> MIX#####.TCH

    This is done simply to shorten the name.

    NODE###.TOP ---> MSG#####.TCH

    This is done to shorten the name as well as give a more accurate
description of what the files are for.

    CHR#####.TCH

    This is not used yet, but will be the new Char By Char data file, described
in NEWCHAT.TXT.  The reason for the name is obvious.

    PRV#####.TCH

    This is a Private Chat data file.  The format is a prototype of the method
described in NEWCHAT.TXT.  The reason for the name is obvious.

    EPR#####.TCH

    This is an Entered Private Chat file, and is used as a flag when a node is
in a private chat.  The reason for the name is obvious.