Port 40bdbef9

Original commit message:
    Int64Mul is lowered to a new turbofan operator, Int32MulPair. The new
    operator takes 4 inputs an generates 2 outputs. The inputs are the low
    word of the left input, high word of the left input, the low word of the
    right input, and high word of the right input. The ouputs are the low
    and high word of the result of the multiplication.

R=ahaas@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1847563003

Cr-Commit-Position: refs/heads/master@{#35143}