Make some nocopy tests a bit more futureproof

Turn the let assignment initializers into move initializers since
that assignment is going to become illegal

src/test/compile-fail/unique-pinned-nocopy.rs

@@ -4,7 +4,7 @@ resource r(b: bool) {
 }
 
 fn main() {
-    let i = ~r(true);
+    let i <- ~r(true);
     let j;
     j = i;
 }

src/test/compile-fail/vec-pinned-nocopy-2.rs

@@ -4,6 +4,6 @@ resource r(b: bool) {
 }
 
 fn main() {
-    let i = [r(true)];
+    let i <- [r(true)];
     i += [r(true)];
 }

src/test/compile-fail/vec-pinned-nocopy-3.rs

@@ -4,7 +4,7 @@ resource r(b: bool) {
 }
 
 fn main() {
-    let i = [r(true)];
+    let i <- [r(true)];
     let j;
     j <- copy [r(true)];
 }

src/test/compile-fail/vec-pinned-nocopy.rs

@@ -4,7 +4,7 @@ resource r(b: bool) {
 }
 
 fn main() {
-    let i = [r(true)];
+    let i <- [r(true)];
     let j;
     j = i;
 }