libgnt/libgnt

2da723f790d6
Use panel_window instead of directly accessing the struct member

This is necessary to fix a FTBFS in Debian. For more information see
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1057570.

Testing Done:
Compiled and ran `test/focus` without issue.

Reviewed at https://reviews.imfreedom.org/r/2883/
[general]
shadow = 0
[colors]
black = 0; 0; 0
red = 1000; 0; 0
green = 0; 1000; 0
blue = 250; 250; 700
white = 1000; 1000; 1000
gray = 700; 700; 700
darkgray = 256; 256; 256
[colorpairs]
normal = black; white
highlight = white; blue
highlightd = black; gray
shadow = black; darkgray
title = white; blue
titled = white; gray
text = white; blue
disabled = gray; white