[AD] ugetx() constness patch and new font subsystem

[Laurence Withers <lwithers@xxxxxxxxxx>]

Hi,

The patch for ugetx() const-correctness has not yet been applied, and I
have a new patch - a rewrite of the font subsystem. A quick summary:

ugetx() patch
 - adds a new function, ugetxc()

 - ugetx() is prototyped as `int ugetx(char**)'

 - ugetxc() is prototype as `int ugetxc(AL_CONST char**)'

 - ugetxc() doesn't have to be implemented; since ugetx and ugetxc are
   actually function pointers, we can simply cast the value of ugetx
   into ugetxc :-)

font subsystem patch
 - allows for extensions to use textout() and family even when they have
   bizarre data structures (such as generated-on-demand).

 - achieved by changing internals of the FONT structure.

 - much grabber code was rewritten; this may have introduced a bug
   here or there. It seems to work 100% ok, however; I did test it
   quite well, but I don't have access to old-format datafiles.

 - adds `int allegro_404_char;' - this is the character used when
   textout() needs to render a string containing a glyph not present
   in the font. Defaults to the `^' caret character, but you can
   change it at runtime. Why? because generate-on-demand fonts may
   have a specific way to render undefined glyphs (eg. truetype fonts  
   use glyph 0).

 - needs to be applied after ugetx() patch.

 - could somebody please reformat it? I still haven't figured out
   Allegro's system...

And a quick note: If you create a font which has glyphs of different
heights, using the current Allegro system, text_height() may return the
wrong height (it returns the height of the first glyph in the first
range). My patch doesn't change this behaviour. Should I fix it?

I haven't posted these (they are too large), so you can grab them from
here:

 http://www.lwithers.demon.co.uk/prog/allegro/patches/

There is a small bit of work left to be done; documentation and (I
think) I wrote this against a pre-ugetx-const-corrected version of
Allegro, so a few ugetx() calls will need to be changed to ugetxc().

Bye for now,
-- 
Laurence Withers, lwithers@xxxxxxxxxx
                http://www.lwithers.demon.co.uk/

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