pushed: Add support for DWARF-based fixed point types

[Joel Brobecker]

> I noticed now that this didn't come with a NEWS entry.
> 
> Shouldn't it have one?  I.e.:
> 
>  - mention that GMP is now a dependency for building GDB
> 
>  - support for fixed point types seems NEWS worthy too
> 
> Also, gdb/README documents configure options and we mention --with-mpfr there.
> Shouldn't we mention --with-libgmp-prefix there too?

Hmmm, indeed on all counts. Thanks for the reminder, Pedro. I will add
that to the list for this weekend.

-- 
Joel