[AD] Allegro on 64-bit platforms

[Eric Botcazou <ebotcazou@xxxxxxxxxx>]

Now that 64-bit computing is becoming mainstream thanks to AMD64, I think it 
is time to make Allegro 64-bit clean.  The library already compiles with GCC 
in strict mode on AMD64/Linux (thanks to Philipp Thomas from SUSE) but I 
don't think it really works.  It also compiles on SPARC64/Solaris.

The first goal is to make it work with GCC.  On 64-bit platforms, GCC is 
almost always LP64 (32-bit int, 64-bit long, 64-bit pointer).  I've attached 
the (purged of noise) result of grep "long" on allegro._tx.  The good news 
is that there are not many problems; but some are deeply rooted in the 
library (e.g. the use of 'long' for 32-bit pixel values).

I think a reasonable approach is to try not to make incompatible changes on 
32-bit platforms and break compatibility as much as we need on 64-bit 
platforms.  We could even think of backporting the work to the stable
branch.

-- 
Eric Botcazou

@@typedef long @fixed
   long size;        - size of file
   long size;     - size of the data in bytes
   unsigned long len;          - length (in samples)
   unsigned long loop_start;   - loop start position
   unsigned long loop_end;     - loop finish position
@@long @ustrtol(const char *s, char **endp, int base);
   Returns the string converted as a value of type `long int'. If nothing was
@@void @rest(long time);
@@void @rest_callback(long time, void (*callback)())
in 32-bit modes sizeof(long) bytes per pixel). You can create and manipulate 
   unsigned long (*BLENDER_FUNC)(unsigned long x, y, n);<endblock>
      ((long *)bmp-&gtline[y])[x] = color;
      bmp_write8((unsigned long)bmp-&gtline[y]+x, color);
unsigned long bmp_write_line(BITMAP *bmp, int line);<br>
unsigned long bmp_read_line(BITMAP *bmp, int line);<br>
unsigned long bmp_unwrite_line(BITMAP *bmp);<br>
coordinate to the returned address. The return value is an unsigned long 
      unsigned long address = bmp_write_line(bmp, y);
      bmp_write8((unsigned long)bmp-&gtline[y]+(x&gt&gt2), color);
   unsigned long screen_base_addr;
   unsigned long loop_start;
   unsigned long loop_end;
@@extern volatile long @midi_pos;
@@extern long @midi_loop_start;
@@extern long @midi_loop_end;
@@long @file_size(const char *filename);
	 long size;        - size of file
@@long @pack_igetl(PACKFILE *f);
   Like pack_getc, but reads a 32-bit long from a file, using Intel byte
@@long @pack_iputl(long c, PACKFILE *f);
   Like pack_putc, but writes a 32-bit long to a file, using Intel byte
@@long @pack_mgetl(PACKFILE *f);
   Like pack_getc, but reads a 32-bit long from a file, using Motorola byte
@@long @pack_mputl(long c, PACKFILE *f);
   Like pack_putc, but writes a 32-bit long to a file, using Motorola byte
@@long @pack_fread(void *p, long n, PACKFILE *f);
@@long @pack_fwrite(const void *p, long n, PACKFILE *f);
@\void @register_datafile_object(int id, void *(*load)(PACKFILE *f, long size),
      long size;     - size of the data in bytes
   Defined to whatever represents a 64-bit "long long" integer for the