STDOUT_FILENO and STDERR_FILENO

[John Emmas <johne53 tiscali co uk>]

Just updated from Git and tried to build libglib using MSVC.  The build 
fails because a couple of files are now referencing 'STDOUT_FILENO' 
and/or 'STDERR_FILENO'.  From the (admittedly, limited) research I did, 
it seemed as if they're only relevant for *nix, bash and Wine.  Here are 
the affected source files in case someone wants to check them:-

        glib/gtestutils.c
        gio/tests/filter-cat.c
        gio/tests/gdbus-eavmple-server.c

That last file (gdbus-example-server.c) does limit its usage so that 
STDOUT_FILENO will only get used if 'G_OS_UNIX' is defined - so maybe 
the others need to be similarly modified?  Thanks.

John