Re: filenaming with .yxx extensions

[Akim Demaille]

| Now, the question is:
| 
|         bison foo.y -d -o foo.x
|            => error (my preferred)
|            => foo.x.c, foo.x.h
|            => foo.c, foo.x.h

or

        bison foo.y -d -o foo.x
             => foo.c, foo.h

i.e., we preserve only the prefix.