9pnet: Adding stats on duration and number of active requests
9pnet: p9_client->conn field is unused. Remove it.
9pnet: trans_fd : allocate struct p9_trans_fd and struct p9_conn together.

There is no point in allocating these structs separately.
Changing this makes the code a little simpler and saves a few bytes of
memory.

This was noticed by Herve Vico.
Added remoteinstall to Makefile
Update statistics output to facilitate parsing.

Total requests: 140761
Total time (us): 11391497
Request duration (us):
          0-255 : 140255
        256-511 : 6
       512-1023 : 2
      1024-2047 : 112
      2048-4095 : 88
      4096-8191 : 115
     8192-16383 : 116
    16384-32767 : 36
    32768-65535 : 22
         65536- : 9
Active requests:
            0-2 : 140761
            3-5 : 0
            6-8 : 0
           9-11 : 0
          12-14 : 0
          15-17 : 0
          18-20 : 0
          21-23 : 0
          24-26 : 0
          27-29 : 0
          30-32 : 0
            33- : 0