Copy stub sysdeps files to other OS impls to reduce compile errors.

sysdeps/openbsd/Makefile.am

@@ -3,7 +3,7 @@ AM_CPPFLAGS			= @AM_CPPFLAGS@
 noinst_LTLIBRARIES		= libgtop_sysdeps-2.0.la libgtop_sysdeps_suid-2.0.la
 
 libgtop_sysdeps_2_0_la_SOURCES	= nosuid.c siglist.c sysinfo.c \
-				  cpu.c loadavg.c \
+				  cpu.c loadavg.c disk.c \
 				  uptime.c netlist.c fsusage.c mem.c \
 				  mountlist.c procopenfiles.c procwd.c \
 				  procaffinity.c glibtop_private.c open.c

sysdeps/openbsd/disk.c

@@ -0,0 +1,42 @@
+/* Copyright (C) 1998-99 Martin Baulig
+   This file is part of LibGTop 1.0.
+
+   Contributed by James Dominic P. Guana <guana.histark@gmail.com>, May 2020.
+
+   LibGTop is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License,
+   or (at your option) any later version.
+
+   LibGTop is distributed in the hope that it will be useful, but WITHOUT
+   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+   for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with LibGTop; see the file COPYING. If not, write to the
+   Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02110-1301, USA.
+*/
+
+#include <config.h>
+#include <glibtop.h>
+#include <glibtop/disk.h>
+
+static const unsigned long _glibtop_sysdeps_disk = 0;
+
+/* Init function. */
+
+void
+_glibtop_init_disk_s (glibtop *server)
+{
+	server->sysdeps.disk = _glibtop_sysdeps_disk;
+}
+
+/* Provides information about disk usage. */
+
+void
+glibtop_get_disk_s (glibtop *server, glibtop_disk *buf)
+{
+	memset (buf, 0, sizeof (glibtop_disk));
+}

sysdeps/openbsd/glibtop_server.h

@@ -41,6 +41,7 @@ G_BEGIN_DECLS
 #define GLIBTOP_SUID_NETLOAD		(1 << GLIBTOP_SYSDEPS_NETLOAD)
 #define GLIBTOP_SUID_PPP		(1 << GLIBTOP_SYSDEPS_PPP)
 #define GLIBTOP_SUID_CPU		0
+#define GLIBTOP_SUID_DISK		0
 #define GLIBTOP_SUID_MEM		0
 #define GLIBTOP_SUID_UPTIME		0
 #define GLIBTOP_SUID_LOADAVG		0