Build 220221

Guess for the amount of work this can count as a new build :) A massive help system overhaul, so 'HELP' is finally helpful:

• The HELP command can now be used in filtered mode (type HELP followed by a few first letters of command(s) and/or switch(es) of interest);
• Highlighting on the HELP screen;
• First-letter quick search (yeah, yeah, I know the command-line switches start with a dash, it does deal with that too so, apparently, in order to find a particular switch you have to press a letter key, not the dash one);
• Improved DUMPHELP command that encodes everything in Windows-friendly manner (no more DOS-specific pseudographics when saving a file).