Expand the definition of gnu89 slightly

[Richard Kenner]

    Add an --enable-pendantic-errors configure option so that these people 
    can have such a thing, if you want.  The people that want it, can use 
    it, the people that don't want to, don't have to.  I do not recommend 
    it being the default.

    This way, you can try and convince your favorite large distributor of 
    gcc to enable it, and then they can get some feedback, and when, let's 
    say, 5 of the biggest distributors do this, we can flip the default 
    from off to on.  If they don't flip it, why should we?

I think it's a *very bad* idea to encourage binary distributions to be
built with different sets of default options.  That would make things
*very* confusing for users.