allegro hardcodes include path for allegro to allegro5

[Mario Domenech Goulart]

Some systems (like Debian) install allegro under /usr/include. The allegro egg should try some common include directory possibilities (like Debian's).

csc -feature compiling-extension -setup-mode    -s -d1 allegro.scm -j allegro -lallegro -lallegro_color -lallegro_image -lallegro_physfs -lallegro_acodec -lallegro_dialog -lallegro_main -allegro_primitives -lallegro_audio -lallegro_font -lallegro_memfile -lallegro_ttf -dumb -lFLAC -lfreetype -logg -lvorbis -lvorbisfile -lz -L/usr/X11R6/lib -L/usr/X11/lib -lGL -LX11 -O3 -C -O3 -D improved-64-bit-support
allegro.c:14:30: fatal error: allegro5/allegro.h: No such file or directory
compilation terminated.

On Debian (testing)

$ head -n 30 /usr/include/allegro.h | tail -n 10

#ifndef ALLEGRO_H
#define ALLEGRO_H

#include "allegro/base.h"

#include "allegro/system.h"
#include "allegro/debug.h"

#include "allegro/unicode.h"