Use native fn's link name attribute if given

Fixes issue #905

Author: lht

src/comp/middle/trans.rs

@@ -5805,9 +5805,15 @@ fn item_path(item: @ast::item) -> [str] { ret [item.ident]; }
 fn collect_native_item(ccx: @crate_ctxt, i: @ast::native_item, &&pt: [str],
                        _v: vt<[str]>) {
     alt i.node {
-      ast::native_item_fn(_, _, _) {
+      ast::native_item_fn(link_name, _, _) {
         if !ccx.obj_methods.contains_key(i.id) {
-            register_native_fn(ccx, i.span, pt, i.ident, i.id);
+            let name =
+              if option::is_some(link_name) {
+                option::get(link_name)
+              } else {
+                i.ident
+              };
+            register_native_fn(ccx, i.span, pt, name, i.id);
         }
       }
       _ { }

src/test/run-pass/native-fn-linkname.rs

@@ -0,0 +1,19 @@
+use std;
+
+import std::vec;
+import std::str;
+
+native "cdecl" mod libc = "" {
+    fn my_strlen(str: *u8) -> uint = "strlen";
+}
+
+fn strlen(str: str) -> uint unsafe {
+    // C string is terminated with a zero
+    let bytes = str::bytes(str) + [0u8];
+    ret libc::my_strlen(vec::unsafe::to_ptr(bytes));
+}
+
+fn main(_args: [str]) {
+    let len = strlen("Rust");
+    assert(len == 4u);
+}