Change InstructionOperand to use a 64-bit field for encoding the operand
information instead of the 32-bit field that was used before. Ideally we
wouldn't use the Zone-allocated bit field at all, and use an integer
instead of the pointer; but that requires fixing the register allocator
first, which will take some time.

TEST=mjsunit/compiler/regress-3786
BUG=v8:3786
LOG=y

Review URL: https://codereview.chromium.org/826673002

Cr-Commit-Position: refs/heads/master@{#25941}