Fix build with compiler defining __i686 (bug 411)

[Roland McGrath]

> +  ".ifndef "GET_PC_THUNK_STR(reg)";"					\

I think it's still our norm to put a space between a macro and its paren,
even for this sort of case.  I also tend towards spaces around the "s.

It's also mostly our norm to use \n in the strings rather than ;,
though that was not done here before.  I think that's much preferable,
as will anyone who ever tries to read a .s file produced from this.


Thanks,
Roland