Fix compiler warnings.

meta-cursor-renderer.c is already fixed upstream in a later release:

Other two files need to be submitted upstream still.

--- mutter-3.18.0/src/backends/meta-cursor-renderer.c Sun Oct 4 19:47:56 2015

+++ mutter-3.18.0/src/backends/meta-cursor-renderer.c Sun Oct 4 19:48:42 2015

@@ -26,6 +26,7 @@

#include "meta-cursor-renderer.h"

+#include <math.h>

#include <meta/meta-backend.h>

#include <meta/util.h>

--- mutter-3.18.0/src/core/window.c Mon Sep 21 12:48:51 2015

+++ mutter-3.18.0/src/core/window.c Tue Jan 5 13:34:16 2016

@@ -3488,7 +3488,7 @@

{

MetaMonitorInfo *info = &window->screen->monitor_infos[i];

- if (info->winsys_id == winsys_id)

+ if ((size_t)info->winsys_id == winsys_id)

return info;

}

@@ -3697,7 +3697,7 @@

meta_window_update_monitor (window, flags & META_MOVE_RESIZE_USER_ACTION);

- if (old_output_winsys_id != window->monitor->winsys_id &&

+ if (old_output_winsys_id != (size_t) window->monitor->winsys_id &&

flags & META_MOVE_RESIZE_MOVE_ACTION && flags & META_MOVE_RESIZE_USER_ACTION)

window->preferred_output_winsys_id = window->monitor->winsys_id;

--- mutter-3.18.1/src/x11/session.c Tue Jan 5 13:40:50 2016

+++ mutter-3.18.1/src/x11/session.c Tue Jan 5 13:41:09 2016

@@ -336,7 +336,7 @@

prop3val.value = &hint;

prop3val.length = 1;

- sprintf (pid, "%d", getpid ());

+ sprintf (pid, "%ld", (long)getpid ());

prop4.name = (char *)SmProcessID;

prop4.type = (char *)SmARRAY8;

prop4.num_vals = 1;