The sha1collisiondetection library by default performs its own "safe-hash"
algorithm, which is not actually the same as the normal SHA-1 algorithm.
For most inputs the output will be the actual SHA-1 hash, but if the input
happens to contain one of several known SHA-1 disturbance vectors this code
returns an alternate "safe-hash" output instead.
This updates the code to explicitly disable "safe-hash" mode and collision
detection, so that we always get actual SHA-1 hashes.