[vtkusers] Some tests fail compiling 5.10.0 on MacOS Cocoa

[David Clunie]

Hi

"make test" after compiling for Cocoa on MacOS 10.8.4 for target 10.7
with Xcode 4.6.2 with architectures "i386;x86_64" had a few failures:

98% tests passed, 5 tests failed out of 299

The following tests FAILED:
      85 - CellLocator (Failed)
     213 - TestAffineWidget (Failed)
     214 - TestButtonWidget (SEGFAULT)
     216 - TestLogoWidget (Failed)
     218 - TestPolyPlane (OTHER_FAULT)

David