Use a larger value type (e.g., 64 bits)

[guowentian]

Hi, I tried to use the ConcurentMap with key as 32bit int and the value as 64 bit int. I test it and there is error saying "misaligned address". I guess the design is just specific to 32 bit key/value, since I noticed the comment line in slab_hash_global.cuh. I am curious that is there any easy workaround to change the code so that I can use the value type of 64 bit int.