[commit] language.h minor cleanup

[Joel Brobecker]

> As far as I know the comment:
> 
> > -/* enum exp_opcode;     ANSI's `wisdom' didn't include forward enum decls. */
> 
> is right, so you shouldn't have comitted this :(.  Perhaps it is now a
> GCC extension to allow these, but as far as I remember older versions
> of GCC didn't accept this.

I thought that we changed the requirement to C90 which should accept this.
I was comforted in this direction by the fact that we already use this
paradigm elsewhere so I thought it was OK.

-- 
Joel