Move flow and function opcodes into their own file

src/opcodes/function.cpp

@@ -0,0 +1,24 @@
+/* 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
+ * General Public License version 2 or any later version.
+ */
+
+#include "sirit/sirit.h"
+#include "opcodes.h"
+
+namespace Sirit {
+
+const Op* Module::Function(const Op* result_type, spv::FunctionControlMask function_control,
+                            const Op* function_type) {
+    Op* op{new Op{spv::Op::OpFunction, bound++, result_type}};
+    op->Add(static_cast<u32>(function_control));
+    op->Add(function_type);
+    return AddCode(op);
+}
+
+const Op* Module::FunctionEnd() {
+    return AddCode(spv::Op::OpFunctionEnd);
+}
+
+} // namespace Sirit