Register a new font loading function.
Informs the load_font() functions of a new file type, providing a routine
to read fonts in this format. The function you supply must follow the
FONT *load_my_font(const char *filename, RGB *pal, void *param)
The pal parameter can optionally be used to return a palette for the FONT.
The parameter param can be anything you like: you can use this to pass
information to your loading routine, such as for instance the font height,
the character range to load or the index number of a font in a datafile.
If you choose to write your own font loading code, your function should be
prepared to deal with a value of NULL for either of these parameters.
The following projects include source code containing this keyword: