convert a few tests from unsafe fns to fns with unsafe bodies

src/test/stdtest/str.rs

@@ -256,7 +256,7 @@ fn unsafe_from_bytes() {
 }
 
 #[test]
-unsafe fn str_from_cstr() {
+fn str_from_cstr() unsafe {
     let a = [65u8, 65u8, 65u8, 65u8, 65u8, 65u8, 65u8, 0u8];
     let b = vec::to_ptr(a);
     let c = str::str_from_cstr(b);
@@ -278,7 +278,7 @@ fn as_buf_small() {
 }
 
 #[test]
-unsafe fn as_buf2() {
+fn as_buf2() unsafe {
     let s = "hello";
     let sb = str::as_buf(s, {|b| b });
     let s_cstr = str::str_from_cstr(sb);

src/test/stdtest/vec.rs

@@ -21,7 +21,7 @@ fn square_if_odd(&&n: uint) -> option::t<uint> {
 fn add(&&x: uint, &&y: uint) -> uint { ret x + y; }
 
 #[test]
-unsafe fn test_unsafe_ptrs() {
+fn test_unsafe_ptrs() unsafe {
     // Test on-stack copy-from-buf.
     let a = [1, 2, 3];
     let ptr = vec::to_ptr(a);