Rename "insts" directory to "instructions"

src/instructions/misc.cpp

@@ -0,0 +1,17 @@
+/* This file is part of the sirit project.
+ * Copyright (c) 2018 ReinUsesLisp
+ * This software may be used and distributed according to the terms of the GNU
+ * Lesser General Public License version 3 or any later version.
+ */
+
+#include "op.h"
+#include "sirit/sirit.h"
+#include <cassert>
+
+namespace Sirit {
+
+Id Module::OpUndef(Id result_type) {
+    return AddCode(std::make_unique<Op>(spv::Op::OpUndef, bound++, result_type));
+}
+
+} // namespace Sirit