* rocshmem_config.h needs to be in a similar directory structure for
includes to work when building testers in build, and from an installed
library
* Do not change installed rocshmem.hpp
* add backend_ipc.{cpp & hpp}
* rename context_ipc.{cpp & hpp} to context_ipc_device.{cpp & hpp}
* add host interface to IPC backend
* add context_ipc_host.{cpp & hpp} to support host interface
* add USE_RO compile flag to enable support for single backend interface at a time
* add ipc_single script to build rocSHMEM with IPC backend
Aurelien Bouteiller
Avinash Kethineedi