Merge: lib/standard/string: Introducting Copy-on-Write FlatBuffers
As requested, implemented a Copy-on-Write mechanism on FlatBuffer, small performance improvement on the to_s operation.
Before :
![cct](https://cloud.githubusercontent.com/assets/1444825/4273670/
fef3f1fc-3cec-11e4-9f81-
8afaa6e4c92a.png)
After :
![concat](https://cloud.githubusercontent.com/assets/1444825/4273675/
028c5bf6-3ced-11e4-93a9-
ef20e94ba55f.png)
Pull-Request: #749
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Jean Privat <jean@pryen.org>