[client] removed the dependency on the ivshmem-server

Since we do not use IRQs anymore we can use the ivshmem-plain device
which doesn't need the ivshmem-server. The QEMU arguments now should be
as follows:

-device ivshmem-plain,memdev=ivshmem
-object memory-backend-file,id=ivshmem,share=on,mem-path=/dev/shm/looking-glass,size=32M

Obviously adjusting the memory size as required. It is suggested that
the shared memory file be created before the guest is started with the
appropriate permissions, for example:

touch /dev/shm/looking-glass
chown user:kvm /dev/shm/looking-glass
chmod 660 /dev/shm/looking-glass

client/Makefile

@@ -17,7 +17,6 @@ CFLAGS  += -DBUILD_VERSION='"$(shell git describe --always --long --dirty --abbr
 OBJS	= main.o \
 	  lg-renderer.o \
 	  spice/spice.o \
-	  ivshmem/ivshmem.o \
 	  renderers/opengl.o
 #	  renderers/opengl-basic.o