- Adds new machine types SimdBool4/8/16 for the different boolean vector types.
- Adds a kSimdMaskRegisters flag for each platform. These are all false for now.
- Removes Create, ExtractLane, ReplaceLane, Equal, NotEqual, Swizzle and Shuffle
  opcodes from the Boolean types. These are unlikely to be well supported natively,
  and can be synthesized using Select.
- Changes the signature of Relational opcodes to return boolean vectors.
- Changes the signature of Select opcodes to take boolean vectors.
- Updates the ARM implementation of Relational and Select opcodes.

LOG=N
BUG=v8:4124

Review-Url: https://codereview.chromium.org/2700813002
Cr-Commit-Position: refs/heads/master@{#43348}