Use ir_function::add_signature to create link between function and signature
ir_function_signature now has a pointer back to the ir_function that owns it.
diff --git a/builtin_function.cpp b/builtin_function.cpp
index 8e7e116..684a10c 100644
--- a/builtin_function.cpp
+++ b/builtin_function.cpp
@@ -214,7 +214,7 @@
ir_variable *declarations[17];
ir_function_signature *const sig = new ir_function_signature(type);
- f->signatures.push_tail(sig);
+ f->add_signature(sig);
ir_label *const label = new ir_label(name);
instructions->push_tail(label);