[FSS0] Add Fusee secondary storage parser

Using "fss0={sd path}" allows you to parse kips, exosphere and warmboot from a fusee secondary binary.

Exosphere and warmboot are overridable if these entries are defined after that.

Additionally any extra kip can be loaded as before via
kip1={sd path}/* for many
or
kip1={sd path} for a sigle one

Warning: Don't double load core kips like loader, pm, sm and ams_mitm. The result will be a hang.

bootloader/hos/fss.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2019 CTCaer
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _FSS_H_
+#define _FSS_H_
+
+#include "hos.h"
+
+int parse_fss(launch_ctxt_t *ctxt, const char *value);
+
+#endif