Fix memory leaks found by ASAN

[NeKzor]

Follow-up of #5

Summary

1.) The switch case statement on SAR_DATA_ENTITY_INPUT_SLOT has a fall-through here:

mdp/src/demo.c

Lines 155 to 158 in 4a580f6

	case SAR_DATA_ENTITY_INPUT_SLOT:
	out->slot = data[0];
	++data;
	case SAR_DATA_ENTITY_INPUT:

but this case is missing in _sar_data_free:

mdp/src/demo.c

Lines 30 to 37 in 4a580f6

	break;
	case SAR_DATA_ENTITY_INPUT:
	free(data.entity_input.targetname);
	free(data.entity_input.classname);
	free(data.entity_input.inputname);
	free(data.entity_input.parameter);
	break;

2.) Missing call to closedir after opendir:

mdp/src/main.c

Lines 301 to 325 in 4a580f6

	DIR *d = opendir(DEMO_DIR);
	if (d) {
	size_t demo_dir_len = strlen(DEMO_DIR);
	struct dirent *ent;
	bool is_first = true;
	while ((ent = readdir(d))) {
	if (!strcmp(ent->d_name, ".")) continue;
	if (!strcmp(ent->d_name, "..")) continue;
	if (!is_first) {
	fputs("\n", g_outfile);
	}
	is_first = false;
	char *path = malloc(demo_dir_len + strlen(ent->d_name) + 2);
	strcpy(path, DEMO_DIR);
	strcat(path, "/");
	strcat(path, ent->d_name);
	_g_detected_timescale = false;
	run_demo(path);
	free(path);
	}

3.) strdup allocated header fields are not freed:

mdp/src/demo.c

Lines 546 to 550 in 4a580f6

	struct demo_hdr hdr = {
	.server_name = strdup((char *)(hdr_buf + 16)),
	.client_name = strdup((char *)(hdr_buf + 276)),
	.map_name = strdup((char *)(hdr_buf + 536)),
	.game_directory = strdup((char *)(hdr_buf + 796)),

mdp/src/demo.c

Lines 84 to 91 in 4a580f6

	void demo_free(struct demo *demo) {
	if (!demo) return;
	for (size_t i = 0; i < demo->nmsgs; ++i) {
	_msg_free(demo->msgs[i]);
	}
	free(demo->msgs);
	free(demo);
	}