Got rid of old gm and rtai code that is no longer used.

src/fe/gm_rcvr/Makefile

src/fe/gm_rcvr/gm_rcvr.c

src/fe/gm_rcvr/manage_network.c

src/fe/rtai_shmem/GNUmakefile

src/fe/rtai_shmem/Makefile

src/fe/rtai_shmem/run

src/fe/rtai_shmem/setup_shmem.c

src/fe/shmem/Makefile

src/fe/shmem/setup_shmem.c

src/fe/test/gm_direct.c

src/fe/test/gm_simple_example.h

src/fe/test/gm_simple_example_recv.c

src/fe/test/gm_simple_example_send.c