fix(macros/generate/convert/auxiliary/c/arguments): Accept newlines

Multiple lines in one comment were not checked for, which resulted in
only one `*` before instead of a new one after every `\n`.

src/macros/generate/convert/auxiliary/c/attribute/mod.rs

@@ -36,7 +36,14 @@ impl Attribute {
             .iter()
             .map(|attr| {
                 if let Attribute::doc(doc_comment) = attr {
-                    format!("*{}\n", doc_comment)
+                    if doc_comment.is_empty() {
+                        "*\n".to_owned()
+                    } else {
+                        doc_comment
+                            .lines()
+                            .map(|line| format!("*{}\n", line))
+                            .collect::<String>()
+                    }
                 } else {
                     attr.to_auxiliary_c()
                 }