We don't need to distinguish between signed and unsigned integral
representations in the big boy type system. It actually even hurts
in some cases. The representation is only about the way the values
are mapped to bits in memory/registers, but the interpretation of
the bits is specified by the semantic dimension.

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/1416953006

Cr-Commit-Position: refs/heads/master@{#31771}