GR_SETUP_ADDRESS, const, GR_INVALID_MSG_RECVD, GR_DOESNT_LOOK_LIKE_A_FD, build.ninja
- macro GR_SETUP_ADDRESS memset/af_unix/memcpy
- constified some vars
- GR_INVALID_MSG -> GR_INVALID_MSG_RECVD
- send/recv -> GR_DOESNT_LOOK_LIKE_A_FD
- build.ninja description musl