So, part two:
The demo then ran fine, a bit jumpy, but that is to be expected from a £20 computer with little processing power! The exscn3d program, the one with all the spinning cubes would run at around 20 fps - is that due to the low processing power on the RPi, or is it just that allegro is not very fast at 3d? All your examples compiled and ran fine then, except:
exrotscl wouldn't open and gave the error message 'Could not load inkblot.tga'
exxfade gave error message 'Error loading image file 'allegro.pcx''
However, exscn3d, which uses allegro.pcx, ran fine.
I then copied the contents of the lib directory into a new directory called allegro.pas in /usr/lib/fpc/2.6.0/units/arm-linux , which is where fpc is installed if you use apt-get. From then everything worked and I just needed to add -ap to compile.