24bit (color)

This adds 24-bit color extensions to rxvt-unicode, mainly so I can use my custom version of Vim in a terminal, but with GUI colorschemes.

Very WIP

Based on the fact that almost every single one of my commits is prefixed with wip (work in progress), you should probably not use this. I've been using it successfully since May, 2013 on a few machines.

Added sequences:

• SGR 38 ; 2 ; {r} ; {g} ; {b} ; m - set foreground color
• SGR 48 ; 2 ; {r} ; {g} ; {b} ; m - set background color
• SGR 38 ; 6 ; {r} ; {g} ; {b} ; m - set default foreground color¹
• SGR 48 ; 6 ; {r} ; {g} ; {b} ; m - set default background color¹
• SGR 38 ; 7 ; {r} ; {g} ; {b} ; m - set cursor foreground color
• SGR 48 ; 7 ; {r} ; {g} ; {b} ; m - set cursor background color

E.g.:

printf '\e[38;7;0;0;255m' - set the cursor foreground to blue

¹: even more incomplete than the rest of this