_hashsplit.c: right shifting 32 bits doesn't work.

_hashsplit.c: right shifting 32 bits doesn't work.

in C, if you do
	uint32_t i = 0xffffffff;
	i >>= 32;

then the answer is 0xffffffff, not 0 as you might expect.  Let's shift it by
less than 32 at a time, which will give the right results.  This fixes a
rare infinite loop when counting the bits in the hashsplit.