Virtualbox 5.0.16 发布可更新下载使用

Virtualbox 5.0.16 发布了，可更新下载使用。

改进记录：

VMM: fixed a problem which could lead to a wrong guest behavior on AMD CPUs (#14831, #15186)
GUI: prevent a crash during startup under rare conditions
GUI: position off-screen windows to be fully visible again on relaunch
PC speaker passthrough: new experimental feature, available on Linux host only
USB: several fixes for the xHCI controller (e.g. for webcam passthrough)
Shared folders: fixed a failure to load the saved state under certain circumstances (#6314)
Added support for (cached) Active Directory authentication in case the domain controller is not reachable (anymore)
Make the Python web service API SDK binding work again (5.0 regression)
Linux hosts: fixed the /sbin/rcvboxdrv script as well as the missing shebang in two scripts (#15055, #15057)
Linux hosts: properly uninstall Python files installed by the .run installer