Fixing failing test cases

Author: eholk

src/test/run-pass/issue-2930.rs

@@ -23,5 +23,5 @@ mod stream {
 fn main() {
     let (bc, _bp) = stream::init();
 
-    stream::client::send(bc, "abc");
+    stream::client::send(bc, ~"abc");
 }

src/test/run-pass/task-comm-16.rs

@@ -33,7 +33,7 @@ fn test_vec() {
 
 fn test_str() {
     let (ch, po) = pipes::stream();
-    let s0 = "test";
+    let s0 = ~"test";
     ch.send(s0);
     let s1 = po.recv();
     assert (s1[0] == 't' as u8);