Merge pull request #13052 from @bendlas

Updates VirtualBox from version 5.0.12 to 5.0.14.

Upstream changes are (without bug IDs):

 * GUI: properly limit the number of VCPUs to the number of physical cores
        on Mac OS X
 * Audio: fixed a bug which prevented loading a saved state of a saved
          guests with HDA emulation (5.0.12 regression)
 * Audio: don't crash if the backend is unable to initialize
 * Audio: fixed audio capture on Mac OS X
 * Storage: fixed a possible crash when attaching the same ISO image
            multiple times to the same VM
 * BIOS: properly report if two floppy drives are attached
 * USB: fixed a problem with filters which would not capture the device
        under certain circumstances (5.0.10 regression)
 * ExtPack: black-list Extension Packs older than 4.3.30 due to
            incompatible changes not being properly handled in the past
 * Windows hosts: fixed a regression which caused robocopy to fail
 * Linux hosts: properly create the /sbin/rcvboxdrv symbolic link (5.0.12
                regression)
 * Mac OS X hosts: several fixes for USB on El Capitan
 * Linux Additions: fixes for Linux 4.5

Full upstream changelog with bug IDs can be found at:

  https://www.virtualbox.org/wiki/Changelog

The reason I was reluctant to merge this before were these symbol lookup
errors:

  vboxsf: Unknown symbol VBoxGuest_RTMemTmpFree (err 0)
  vboxsf: Unknown symbol VBoxGuestIDCCall (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTSemFastMutexRequest (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTSemFastMutexRelease (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTLogRelGetDefaultInstanceEx (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTErrConvertToErrno (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTSemFastMutexCreate (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTSemFastMutexDestroy (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTMemContFree (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTSemMutexRelease (err 0)
  vboxsf: Unknown symbol VBoxGuestIDCOpen (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTAssertShouldPanic (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTMemContAlloc (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTSemMutexRequest (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTSemMutexCreate (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTMemTmpAllocTag (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTSemMutexDestroy (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTAssertMsg1Weak (err 0)
  vboxsf: Unknown symbol VBoxGuestIDCClose (err 0)
  vboxsf: Unknown symbol VBoxGuest_RTAssertMsg2Weak (err 0)

However, after testing it against 5.0.12, the same errors occur there as
well, so it is likely related to our VM tests.