Fix Coverity CIDs 1356044 and 1356045 Unintended sign extension

[truckman]

Summary

When shifting an unsigned byte into the upper 8 bits of
an int and the resulting value is greater than 0x7FFFFFF,
the result will be sign extended when converting to a 64
bit unsigned long.

[ken]

Looks good, thank you!

[truckman]

Closed by commit rS300686: Fix a couple of Coverity Unintended sign extension sign extension (authored by truckman).