Modifying reg_names

[Richard Kenner]

    Your patch of Fri May 19 18:16:31 2000 that constifies the reg_names
    array breaks gcc targets that use CONDITIONAL_REGISTER_USAGE to modify
    the register names.  Was this unintentional or do you have another
    scheme that can be used?

I didn't constify it, but merely made things consistent with other places that
did do it to avoid warnings.

It sounds like it should *not* have been const and the proper fix would have
been to make it *not* be const everywhere instead of being const.  So that
seems the right fix to me.