This patch adds struct multi_client_states for managing multiple clients
and adds gdb_fildes_t support to routines write_prim, read_prim, readchar
for handling client specific io,with each client associated with its
corresponding file desc.   Thispatch adds the corresponding file desc to
the client_state and adds afile desc parameter to the gdbserver I/O ops.
It also adds structmulti_client_states which currently just manages a 
primary
client_statebut will later allow managing  a collection of client_states
where each client_state is the state for an individualclient.  This patch
defines get_client_state using multi_client_statesdefines.  Concurrent with
this patch is an strace patch that adds a gdbserver backend to strace.

Add struct multi_client_states

* server.h (struct multi_client_states):  New.
* server.c (g_client_states)
   (get_client_states, multi_client_sates::add_client_state):  New.
   (captured_main):  Set multi_client_states.client_states
* remote-utils.c (gdb_connected, remote_prepare, remote_close)
   (putpkt_binary_1, getpkt)  Use client_state.remote_desc.
   (handle_accept_event):  Set the client state for this remote file  desc.
   (write_prim, read_prim, readchar): Add gdb_fildes_t parameter.
    Change all callers.