[AD] Filters patch to allegro-4.1.4

[Gareth Bushell <garth@xxxxxxxxxx>]

Hi

here http://www.garthy.com/allegro-5/allegro.html is a work in progress 
to convert allegro to use filters as disscussed in alleg5 mailing list. 
This patch implements reading of uncompressed datafiles. There are still 
many problems but I've decided to put the code out for public review on 
the allegro development list and allegro 5 list. Comments/suggestions 
are welcome. I'm at present working on write support and hopefully this 
won't be too far away. There also needs to be compression support added 
to al_alcompress. To install this patch follow instaructions below. Have 
fun!

1. untar the source
2. untar a clean copy of allegro-4.1.4
3. change to the al_filters directory created by step 1.
4. run the install.sh script passing it the directory allergo-4.1.4 is
in eg:-

install.sh ~/allegrto-4.1.4

5. Configure allegro

./configure --enable-dbglib --enable-dbgprog

This has only been tested with debug build as ASSERTS catch places where
code isn't written yet so the above configure line is recomended!!!!

6. Open a "Non-compressed" datafile" (you may have to create one with 
the non-patched allegro grabber first!)

7. Stand back in awe at the clean up that has occoured to pack_fopen and
     friends by being converted to use filters. ;-)

Took a while but had to move house and had broadband installation and
email trouble.

Enjoy

Garth

P.S. May post a demo of allegro transparantly loading a datafile over a
network from the grabber!! Great for client server games that need to
load resources from the server. If you want this mail me(+list) to show
demand! the infrastructure is already there (filter_net* files)