Update to 10.1.15

Changelog:
* Add entries for MacOS 10.13 (High Sierra) to guest_os_tables.h.
* Report version data via guestinfo vars.
* For FreeBSD 11 and later the correct osname is "freeBSD11".
* Tools Hgfs Plugin: refresh Hgfs drives on client start
* If for some reason RandR12GetInfo failed to return RandR12Info,
  should not follow the cleanup path to free it. Instead it
  should return FALSE.

(ryoon)