/home/anoyes/workspace/foundationdb/flow/DeterministicRandom.cpp:72:29: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
This will allow me to recompile faster after making changes, and should
(slightly) speed up overall compilation.
I manually verified that the unseed matched for one test before and
after this change, so I probably didn't screw up the refactor
