Color terminal?

[Michael Goffioul]

Hi,

While I'm at terminal-related stuff, I hacked octave a little bit such that
it can make use of colored terminal. It includes:
- additional --color argument to turn it on (turned off by default)
- internal boolean Vterminal_color variable to hold the state
- surround the prompt string with control chars to make it appear blue;
the same with error strings to make it appear red (the color could be made
configurable, if needed).

The whole stuff uses ANSI terminal color control sequence (I don't if
there are still many terminal emulation out there that wouldn'tn support
it). Would you like me to provide a patch?

Michael.