toolchain: add a program for compiling ipc interface definitions

ifc can be used to compile .if files into self-contained header-only C
libraries, which can be used to send/receive messages that conform
to the described interface.

toolchain/ifc/type.h

@@ -0,0 +1,17 @@
+#ifndef IFC_TYPE_H_
+#define IFC_TYPE_H_
+
+enum type_id {
+	TYPE_NONE,
+	TYPE_INT,
+	TYPE_STRING,
+	TYPE_OTHER,
+};
+
+struct type {
+	enum type_id ty_id;
+};
+
+extern void type_print(const struct type *ty);
+
+#endif