Update V8

Update V8

Fixes a bug in threadsafe symbol id generation, and adds a ComputeHash
implementation for const char * strings.

Change-Id: Id1fb4c7d9bf8eae59229b3893e8a9ef20dede336
Reviewed-on: http://codereview.qt.nokia.com/1621
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>
Reviewed-by: Simon Hausmann <simon.hausmann@nokia.com>