[FYI 0/3] trivial unused fixes

[Tom Tromey <tromey at redhat dot com>]

I'm checking these in.

Two of these patches just remove declarations that no longer have
corresponding definitions.

The third removes the "use_windows" global and the corresponding field
from struct capture_main_args.  I had long assumed that this was used
by Insight, but recently I checked the sources and I found that
nothing checks this variable.

Tested by rebuilding and grep.

Tom