util/mem: Move memdup to new util/mem.c file

This seems handy and I want to use this in wlr_color_representation.

util/mem.c

@@ -0,0 +1,16 @@
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "util/mem.h"
+
+bool memdup(void *out, const void *src, size_t size) {
+	void *dst = malloc(size);
+	if (dst == NULL) {
+		return false;
+	}
+	memcpy(dst, src, size);
+	void **dst_ptr = out;
+	*dst_ptr = dst;
+	return true;
+}

util/meson.build

@@ -6,6 +6,7 @@ wlr_files += files(
 	'global.c',
 	'log.c',
 	'matrix.c',
+	'mem.c',
 	'rect_union.c',
 	'region.c',
 	'set.c',