fix unit test warnings

[bashbaug]

Fixes new warnings in the unit tests:

14>D:\git\OpenCL-CLHPP\tests\test_openclhpp.cpp(1862,50): warning C4312: 'type cast': conversion from 'unsigned int' to 'void *' of greater size

This change follows the existing pattern for converting from a specific bit pattern to a void*.

edit: also fix a few warnings relating to the signature of a few new test functions:

'void (__cdecl *)()' differs in parameter lists from 'UnityTestFunction'

The test functions need to specifically say that their arguments are void.