clients & tests: Unify multiple definitions of x*alloc and related functions

Direct fail_on_null calls now produce output like:

    [weston-info] clients/weston-info.c:714: out of memory

xmalloc, et al produce output on failure like:

    [weston-info] out of memory (-1)

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/clients/multi-resource.c b/clients/multi-resource.c
index 4ed4d50..b061e68 100644
--- a/clients/multi-resource.c
+++ b/clients/multi-resource.c
@@ -40,6 +40,7 @@
 
 #include <wayland-client.h>
 #include "shared/os-compatibility.h"
+#include "shared/xalloc.h"
 #include "shared/zalloc.h"
 
 struct device {
@@ -83,20 +84,6 @@
 	buffer_release
 };
 
-static inline void *
-xzalloc(size_t s)
-{
-	void *p;
-
-	p = zalloc(s);
-	if (p == NULL) {
-		fprintf(stderr, "%s: out of memory\n", program_invocation_short_name);
-		exit(EXIT_FAILURE);
-	}
-
-	return p;
-}
-
 static int
 attach_buffer(struct window *window, int width, int height)
 {