Graphene IPC (GIPC) was introduced to perform faster bulk IPC by sharing pages as copy-on-write
across processes. This feature became stale, and it was shown that recent Linux kernels (4.2+)
have zero-copy transfers over UNIX sockets and exhibit similar performance. GIPC is not built and
not tested in Jenkins. Also, GIPC does not work under SGX. This commit completely removes GIPC.