Fix path to config.c in sesman/tools/Makefile.am
Fix sound and clipboard crashes

- In case clipboard is not initialized, clipboard_data_in returns
    (fixes a segfault)
- If less than 4 bytes are sent to sound_send_wave_data_chunk, it
  returns
    (fixes a segfault)
- When sending sound initiliazation messages set g_chan in chansrv to 0,
  so the server waits for client to reply (this makes sound work afte
  reconnecting)
- In process_message_channel_setup, clear any leftover data in
  chan_items