Graphene and secp256k1-zkp

[bytemaster]

https://github.com/cryptonomex/graphene/issues/76

[maqifrnswa]

I see that the secp256k1-zkp library has configuration options hard coded instead of using the ./configure script:
https://github.com/cryptonomex/fc/blob/master/CMakeLists.txt
https://github.com/ElementsProject/secp256k1-zkp

That is causes build errors on some systems:
In file included from /home/pi/graphene/graphene/libraries/fc/vendor/secp256k1-zkp/src/secp256k1.c:11:0:
/home/pi/graphene/graphene/libraries/fc/vendor/secp256k1-zkp/src/util.h:102:37: error: ‘__int128’ is not supported for this target
 SECP256K1_GNUC_EXT typedef unsigned __int128 uint128_t;

since not all architectures have __int128

just running ./autogen.sh and ./configure then make works in that folder, but the fc cmake build does not work

I know it's early and it's probably just set up for testing at this point, but I wanted to give a heads up.