usage of openssl

[bitmarkcc]

There are some problems with how openssl is used.

In bignum.h the BIGNUM *bn data member of CBigNum, is referenced by overloading the ampersand (&) operator. This can lead to unpredictable behavior (https://www.appmarq.com/public/changeability,8010,Do-not-overload-the-ampersand-comma-logical-AND-or-logical-OR-operators). Also, util.h does not need to be included.

The usage of ECDSA_SIG_get0 is not ideal... There also needs to be a call to ECDSA_SIG_set0 for openssl versions >= 1.01 when initializing the ECDSA sig (this leads to an error in one of the unit tests).

Solution: bitmarkcc@799f18c