Complete rewrite of the error code generation script. It now runs as a single

Complete rewrite of the error code generation script. It now runs as a single
script, translates function codes better and doesn't need the K&R function
prototypes to work (NB. the K&R prototypes can't be wiped just yet: they are
still needed by the DEF generator...). I also ran the script with the -rewrite
option to update all the header and source files.