This patch adds support for special underlines. It allows the use of the following SGR parameters:
- 4:x - Where x can be 0 (No underline), 1-2 (Straight), 3 (Curly/Wavy)
- 58:5:x - Where x is the index of one of the terminal colors, up to 255, that the underline will be drawn with.
- 58:2:r:g:b - Where r, g and b are the red, green and blue color values of the underline respectively.
- 59 - Resets the underline color to the foreground color.
These escape codes aren't standard, but they are supported by most other terminal emulators, as well as many terminal programs (Such as Vim).