Portable int64 Literals

[njwhite]

I was getting:

[ 45%] Generating GpuInitGroups.o
/Users/nwhite/mapd.git/QueryEngine/GpuInitGroups.cu(126): error: no instance of function template "fill_empty_device_key" matches the argument list
            argument types are: (int64_t *, const uint32_t, long)

1 error detected in the compilation of "/tmp/tmpxft_0000621a_00000000-7_GpuInitGroups.cpp1.ii".
make[2]: *** [QueryEngine/GpuInitGroups.o] Error 2
make[2]: *** Waiting for unfinished jobs....
/Users/nwhite/mapd.git/QueryEngine/GpuInitGroups.cu(126): error: no instance of function template "fill_empty_device_key" matches the argument list
            argument types are: (int64_t *, const uint32_t, long)

1 error detected in the compilation of "/tmp/tmpxft_0000621b_00000000-7_cuda_mapd_rt.cpp1.ii".
make[2]: *** [QueryEngine/cuda_mapd_rt.o] Error 2
make[1]: *** [QueryEngine/CMakeFiles/QueryEngine.dir/all] Error 2

...on OSX using clang-800.0.42.1 & nvcc Cuda compilation tools, release 8.0, V8.0.61. More CMake logs available if needed!

[asuhan]

Thanks, looks good. I'll merge as soon as you sign the CLA.

[njwhite]

@asuhan sent my signed CLA to contributors@mapd.com!