Error reported by debug mode when running sstable test
Solution is to use unaligned cast.
dht/murmur3_partitioner.cc:67:25: runtime error: load of misaligned
address 0x6030000478fc for type 'const long int', which requires 8
byte alignment
Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>