Update ChangeLog for 1.2.

https://code.google.com/p/esprima/issues/detail?id=514
Stable version 1.2.0.

https://code.google.com/p/esprima/issues/detail?id=514
Branch 1.x is for 1.3 development.

https://code.google.com/p/esprima/issues/detail?id=535