EIP-145 Bitwise Shift

Documentation for tests/constantinople/eip145_bitwise_shift@0c700940.

Generate fixtures for these test cases for Prague with:

fill -v tests/constantinople/eip145_bitwise_shift --fork Prague

abstract: Test EIP-145: Bitwise shifting instructions in EVM.

Tests for  [EIP-145: Bitwise shifting instructions in EVM](https://eips.ethereum.org/EIPS/eip-145).