Add 80125

Issue: rust-lang/rust#80125

Author: fanninpm

ices/80125.rs

@@ -0,0 +1,16 @@
+type ExternCallback = extern "C" fn(*const u8, u32, str);
+
+pub struct Client {
+    // ...
+    conn_tx_bind: ExternCallback,
+    // ...
+}
+
+#[no_mangle]
+pub extern fn register_something(bind: ExternCallback) -> Client {
+    Client{
+        conn_tx_bind: bind
+    }
+}
+
+fn main() {}