Fix shl/shr for negative Integers, remove unnecessary stuff from js.bn.
Fix shl/shr for negative Integers, remove unnecessary stuff from js.bn.

nyson/haste-compiler,kranich/haste-compiler,kranich/haste-compiler,nyson/haste-compiler,nyson/haste-compiler,kranich/haste-compiler,nyson/haste-compiler,kranich/haste-compiler