tc class: Show classes as ASCII graph

tc class: Show classes as ASCII graph

Added new '-g[raph]' option which shows classes in the graph view.

Meanwhile only generic stats info output is supported.

e.g.:

$ tc/tc -g class show dev tap0
+---(1:2) htb rate 6Mbit ceil 6Mbit burst 15Kb cburst 1599b
|    +---(1:40) htb prio 0 rate 5Mbit ceil 5Mbit burst 15Kb cburst 1600b
|    +---(1:50) htb rate 3Mbit ceil 6Mbit burst 15Kb cburst 1599b
|    |    +---(1:51) htb prio 0 rate 1Kbit ceil 6Mbit burst 15Kb cburst 1599b
|    |
|    +---(1:60) htb prio 0 rate 1Kbit ceil 6Mbit burst 15Kb cburst 1599b
|
+---(1:1) htb rate 6Mbit ceil 6Mbit burst 15Kb cburst 1599b
     +---(1:10) htb prio 0 rate 5Mbit ceil 5Mbit burst 15Kb cburst 1600b
     +---(1:20) htb prio 0 rate 3Mbit ceil 6Mbit burst 15Kb cburst 1599b
     +---(1:30) htb prio 0 rate 1Kbit ceil 6Mbit burst 15Kb cburst 1599b

$ tc/tc -g -s class show dev tap0
+---(1:2) htb rate 6Mbit ceil 6Mbit burst 15Kb cburst 1599b
|    |    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
|    |    rate 0bit 0pps backlog 0b 0p requeues 0
|    |
|    +---(1:40) htb prio 0 rate 5Mbit ceil 5Mbit burst 15Kb cburst 1600b
|    |          Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
|    |          rate 0bit 0pps backlog 0b 0p requeues 0
|    |
|    +---(1:50) htb rate 3Mbit ceil 6Mbit burst 15Kb cburst 1599b
|    |    |     Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
|    |    |     rate 0bit 0pps backlog 0b 0p requeues 0
|    |    |
|    |    +---(1:51) htb prio 0 rate 1Kbit ceil 6Mbit burst 15Kb cburst 1599b
|    |               Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
|    |               rate 0bit 0pps backlog 0b 0p requeues 0
|    |
|    +---(1:60) htb prio 0 rate 1Kbit ceil 6Mbit burst 15Kb cburst 1599b
|               Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
|               rate 0bit 0pps backlog 0b 0p requeues 0
|
+---(1:1) htb rate 6Mbit ceil 6Mbit burst 15Kb cburst 1599b
     |    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
     |    rate 0bit 0pps backlog 0b 0p requeues 0
     |
     +---(1:10) htb prio 0 rate 5Mbit ceil 5Mbit burst 15Kb cburst 1600b
     |          Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
     |          rate 0bit 0pps backlog 0b 0p requeues 0
     |
     +---(1:20) htb prio 0 rate 3Mbit ceil 6Mbit burst 15Kb cburst 1599b
     |          Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
     |          rate 0bit 0pps backlog 0b 0p requeues 0
     |
     +---(1:30) htb prio 0 rate 1Kbit ceil 6Mbit burst 15Kb cburst 1599b
                Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
                rate 0bit 0pps backlog 0b 0p requeues 0

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>