How to write a font file.

The first two values are the width and the height of the
characters. The next value is the number of images in which we take
the characters, followed by the image resources.

The remaining of the file consists in a description of the
characters. Each line has four fields. The first one is the character,
then come the X and Y position of the character in the image. The last
field is the zero-based index of the image resource where the
character is, in the list defined before.

There must be no empty lines between the image resources and the lines
describing the characters.
