Core: Fix a bug in BigNumber::SetQword
Core: Fix a bug in BigNumber::SetBinary
Fix BigNumber::AsByteArray function by returning Auto_Ptr.

Remove mutex from BigNumber class - it didn't do what it was advertised to do - consider using the "locked" array outside of the function in which it was "locked".
Fix crashed caused by using openssl from multiple threads simultanously.

Note that this doesn't make BigNumber class threadsafe - it never was that way.