clients/simple-damage,simple-shm: Use calloc instead of malloc

This avoids some unwarranted errors about conditional jumps or
invalid access from ASan as malloc doesn't set the memory to zero.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

clients/simple-damage.c

@@ -774,7 +774,7 @@ create_display(int version)
 {
 	struct display *display;
 
-	display = malloc(sizeof *display);
+	display = zalloc(sizeof *display);
 	if (display == NULL) {
 		fprintf(stderr, "out of memory\n");
 		exit(1);

clients/simple-shm.c

@@ -396,7 +396,7 @@ create_display(void)
 {
 	struct display *display;
 
-	display = malloc(sizeof *display);
+	display = zalloc(sizeof *display);
 	if (display == NULL) {
 		fprintf(stderr, "out of memory\n");
 		exit(1);