IVRSystem missing from libopenvr_api_64.so -- VRInitError_Init_InterfaceNotFound

[mncharity]

libopenvr_api_64.so currently does not contain the IVRSystem interface.

$ cd src/openvr/
$ grep IVRSystem libopenvr_api_*
Binary file libopenvr_api_32.dll matches
Binary file libopenvr_api_64.dll matches
$ strings libopenvr_api_64.so | grep _0
# ... a shorter list of interfaces than in .dll ...

Without IVRSystem, even VRApplication_Utility fails with VRInitError_Init_InterfaceNotFound.

$ cat x02.py
import sys
import time
import openvr

openvr.init(openvr.VRApplication_Utility)
openvr.shutdown()

$ python x02.py
Traceback (most recent call last):
  File "x02.py", line 5, in <module>
    openvr.init(openvr.VRApplication_Utility)
  File "/usr/local/lib/python2.7/dist-packages/openvr/__init__.py", line 5049, in init
    return VRSystem()
  File "/usr/local/lib/python2.7/dist-packages/openvr/__init__.py", line 1709, in VRSystem
    return _internal_module_context.VRSystem()
  File "/usr/local/lib/python2.7/dist-packages/openvr/__init__.py", line 1627, in VRSystem
    self.m_pVRSystem = IVRSystem()
  File "/usr/local/lib/python2.7/dist-packages/openvr/__init__.py", line 1845, in __init__
    _checkInitError(VRInitError_Init_InterfaceNotFound)
  File "/usr/local/lib/python2.7/dist-packages/openvr/__init__.py", line 5033, in _checkInitError
    raise OpenVRError("%s (error number %d)" %(getVRInitErrorAsSymbol(error), error))
openvr.OpenVRError: VRInitError_Init_InterfaceNotFound (error number 105)