Contained in here is a list of VT100 facilities (and extension based on it),
that have very low priority or are not likely to be ever implemented by me.
The order is more or less by priority, so you'll find the most interesting
stuff in the beginning. All this is mainly included so that you can see, what
you miss.

- some modes -----------------------------------------------------------------

 The next two modes are difficult to implement (for me).
 May be i do them, may be not. Think, smooth scroll would be kool.

   '?4'= Jump scroll (set); Smooth scroll (reset)
   '?8'= Auto repeat on (set); Auto repeat off (reset)

 following are not in VT100, nor in xterm, check Linux console

    '2'= Lock keyboard (set); Unlock keyboard (reset)
   '12'= Echo on (set); Echo off (reset)

Hmm, one can easily dig out more other which may originate from different
VT100/VT102 variants. We'll keep things simple, but have to check trough xterm
and Linux console to be sure.

- rendition material ----------------------------------------------------------

This is mainly not implemented because the fonts are too weak.
Eventually, i can do better if i dig a little...
 
Set graphic rendition
  Where <n> is
   2 = Half				// Not in vt100, ansi italic
  21 = Normal intensity (this might well be a spelling mistake i.e. == 22)
  Check linux console for some sco-ish stuff.
 
Line attributes
  Double-height Top half      Esc  #   3
                Bottom half   Esc  #   4
  Single-width, single-height Esc  #   5
  Double-width                Esc  #   6

- printing related stuff, will not be implemented ----------------------------

Don't think this is of any use today. 
These codes seem not to appear in VT100 only, may be it was an option.
Implement a log instead?
Implement "save screen and buffer"?

Modes // not in VT100
  '?18'= Send FF to printer after print screen (set); No char after PS (reset)
  '?19'= Print screen prints full screen (set); PS prints scroll region (reset)
 
Printing
  Esc  [ <c> i
  Where <c> is
      ''= Same as '0'
     '0'= Prints screen (full or scroll region)
     '4'= Printer controller off
     '5'= Printer controller on (Print all received chars to printer)
    '?1'= Print cursor line
    '?4'= Auto print off
    '?5'= Auto print on (Prints line to printer when you exit from it)
 
VT52 sequences
    Auto print on          Esc  ^
    Auto print off         Esc  -
    Printer controller on  Esc  W
    Printer controller off Esc  X
    Print cursor line      Esc  V
    Print screen           Esc  ]

- huh, that could be fun! ----------------------------------------------------
 
Programmable LEDs               Esc [ Ps q
        0 - All LEDs off
  (1 - 4) - Turn respective LED on
 
- does not produce a reply, anyway -------------------------------------------

Invoke confidence test
    Esc  [   2   ; <n> y
  Where <n> is
     '1'= Power-up test
     '2'= Data loopback test
     '4'= EIA loopback test
     '9'= Power-up tests (continuously)
    '10'= Data loopback tests (continuously)
    '12'= EIA loopback tests (continuously)
    '16'= Printer loopback test
    '24'= Printer loopback tests (continuously)