Reflect latest interface changes; return 0 on success and -1 on error.

sysdeps/linux/prockernel.c

@@ -37,6 +37,8 @@ int
 glibtop_init_proc_kernel_s (glibtop *server)
 {
 	server->sysdeps.proc_kernel = _glibtop_sysdeps_proc_kernel;
+
+	return 0;
 }
 
 /* Provides detailed information about a process. */
@@ -51,10 +53,10 @@ glibtop_get_proc_kernel_s (glibtop *server, glibtop_proc_kernel *buf, pid_t pid)
 	memset (buf, 0, sizeof (glibtop_proc_kernel));
 
 	if (proc_stat_to_buffer (buffer, pid))
-		return;
+		return -1;
 
 	p = proc_stat_after_cmd (buffer);
-	if (!p) return;
+	if (!p) return -1;
 
 	p = skip_multiple_token (p, 6);
 
@@ -74,4 +76,6 @@ glibtop_get_proc_kernel_s (glibtop *server, glibtop_proc_kernel *buf, pid_t pid)
 	buf->nwchan = strtoul (p, &p, 0);
 
 	buf->flags = _glibtop_sysdeps_proc_kernel;
+
+	return 0;
 }