Modernize solaris threads support.

[Eli Zaretskii]

> Cc: Pedro Alves <pedro@codesourcery.com>, gdb-patches@sourceware.org
> From: Tom Tromey <tromey@redhat.com>
> Date: Tue, 17 Feb 2009 13:00:31 -0700
> 
> >>>>> "Eli" == Eli Zaretskii <eliz@gnu.org> writes:
> 
> Perdo> If you still want those declarations for some reason, I'll
> Pedro> put them back.
> 
> Eli> Please do, and thanks.
> 
> Please also provide your rationale.
> We know Pedro's, but we don't know yours.

It's a matter of personal preferences, that's why I didn't explain it
in the first place.  I prefer to have the prototypes because that
avoids problems when functions are rearranged so that some are used
before they are defined.

I also dislike gratuitous changes in code that is there for at least 9
years.

As long as these preferences don't contradict GNU coding conventions
and guidelines, I'd like to stick to them.