[openssl-dev] [openssl.org #4257] Fix BN_gcd errors for curves with even order that do not play nicely with Montgomery arithmetic

[Billy Brumley via RT]

https://github.com/openssl/openssl/pull/571

I was getting errors for curves with even order. This patch squelches
the errors.

139858767824544:error:0306E06C:lib(3):func(110):reason(108):bn_gcd.c:233:
139858767824544:error:0306E06C:lib(3):func(110):reason(108):bn_gcd.c:233: