Converting INT_MIN to positive should cause overflow,
which was not being captured. Fixed the logic to detect
if value is equal to INT_MIN and set the overflow code
accordingly.

R=joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2446113013
Cr-Commit-Position: refs/heads/master@{#40631}