Gankro/rust — pull request #2 by cuviper (2014-12-10 20:19:17+00:00)
Title: bitv: Avoid undefined behavior in mask_for_bits

It was relying on the fact that x86 shifts are effectively %BITS, so
shifting a u32 by 32 preserves all bits. But this is undefined behavior
in general. Add an explicit %BITS to be safe.