core/std: whitespace fixes.

src/libstd/io.rs

@@ -508,6 +508,7 @@ fn mem_buffer_buf(b: mem_buffer) -> [u8] { vec::from_mut(b.buf) }
 fn mem_buffer_str(b: mem_buffer) -> str {
     let b_ = vec::from_mut(b.buf);
     str::from_bytes(b_)
+}
 
 fn with_str_writer(f: fn(writer)) -> str {
     let buf = mk_mem_buffer();