True Color (24 bit) or 16 million colors support

Here's a test case:

printf "\x1b[38;2;255;100;0mTRUECOLOR\x1b[0m\n"

* or http://github.com/robertknight/konsole/tree/master/tests/color-spaces.pl
* or https://git.gnome.org/browse/vte/tree/perf/img.sh?h=vte-0-36

According to Wikipedia[1], this is only supported by xterm and konsole.

It's a common confusion about terminal colors... Actually we have this:
* plain ascii
* ansi escape codes (16 color codes with bold/italic and background)
* 256 color palette (216 colors+16gray + ansi) (colors are 24bit)
* 24bit true color (888 colors (aka 16 milion)

The 256 color palete is configured at start, and it's a 666 cube of
colors, each of them defined as a 24bit (888 rgb) color.

This means that current support can only display 256 different colors
in the terminal, while truecolor means that you can display 16 milion
different colors at the same time.

Truecolor escape codes doesnt uses a color palete. It just specifies the
color itself.

[1] https://en.wikipedia.org/wiki/ANSI_color

Here are terminals discussions:
==============================

Now supporting truecolor
------------------------

* st (from suckless) -  http://lists.suckless.org/dev/1307/16688.html
* konsole - https://bugs.kde.org/show_bug.cgi?id=107487
* iterm2 - https://code.google.com/p/iterm2/issues/detail?id=218
* all libvte based terminals:  https://bugzilla.gnome.org/show_bug.cgi?id=704449
    * Gnome Terminal
    * sakura
    * Terminator
    * Lilyterm
    * ROXTerm
    * evilvte
    * Termit
    * Tilda
    * stjerm
    * tinyterm
    * GTKTerm2

Parsing ANSI color sequences, but approximating them to 256 palette:
--------------------------------------------------------------------

* xterm
* mlterm - http://sourceforge.net/mailarchive/message.php?msg_id=31828705

NOT supporting truecolor:
-----------------------------

* urxvt -  http://lists.schmorp.de/pipermail/rxvt-unicode/2013q3/001826.html 
* Terminlogy (E17) - https://phab.enlightenment.org/T746
* mrxvt - https://sourceforge.net/p/materm/feature-requests/41/
* aterm - https://sourceforge.net/p/aterm/feature-requests/23/
* fbcon (from linux kernel) - https://bugzilla.kernel.org/show_bug.cgi?id=79551 
* FreeBSD console - https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=191652 

Here are another console programs discussions:
============================================

* mutt - http://dev.mutt.org/trac/ticket/3674
* mc - http://www.midnight-commander.org/ticket/3145#comment:1
* s-lang library - http://lists.jedsoft.org/lists/slang-users/2014/0000001.html
* ncurses library - 
https://lists.gnu.org/archive/html/bug-ncurses/2013-10/msg00007.html
* mcabber - 
https://bitbucket.org/McKael/mcabber-crew/issue/126/support-for-true-color-16-mi
llions-colors
* emacs - 
http://emacs.1067599.n5.nabble.com/RFC-Add-tty-True-Color-support-td299962.html
* vim - https://bitbucket.org/ZyX_I/vim/commits/branch/24-bit-xterm
* tig - https://github.com/jonas/tig/issues/227
Original issue reported on code.google.com by xvi...@gmail.com on 6 Jul 2014 at 11:04
lcy19870112 / mintty

True Color (24 bit) or 16 million colors support #431
