MSVC 2015 cannot build fullpipe/director in x64, SCUMM_64BITS missing

[quietust]

Both the "Director" and "Fullpipe" engines expect SCUMM_64BITS to be defined for their Pointer_Hash class to work correctly, and this is only defined by the CMake backend for create_project, not MSBuild; as a result, builds fail due to being unable to cast "const void *" to "uint".

Current commit: 5be720cdebe4ccb10fbb09c8d57bcdb2ef155c93

[Templier]

Thank you for the report!

Fixed slightly differently from the patch by adding the define to ScummVM_Global64.props so it works with both MSBuild and old-style VS projects