modmul operation returns wrong results for negative numbers

[Slava0135]

Current Behavior

For negative numbers operation returns wrong results (compared to C#).

100 * -1 % -91 == 82

Expected Behavior

C# results:

100 * -1 % -91 == -9

Possible Solution

Steps to Reproduce

1. ./bin/neo-go vm
2. loadbase64 AGQA/wClpQ==
3. run

Your Environment

• Version of the product used: master (c960a7e)