Writes the string `s' onto the bitmap at position x, y, using the
specified font, foreground color and background color. If the background
color is -1, then the text is written transparently. If the foreground
color is -1 and a color font is in use, it will be drawn using the colors
from the original font bitmap (the one you imported into the grabber
program), which allows multicolored text output. For high and true color
fonts, the foreground color is ignored and always treated as -1. Example:
/* Show the program's version in blue letters. */
textout_ex(screen, font, "v4.2.0-beta2", 10, 10,
makecol(0, 0, 255), -1);
