Gas calculation in tracer

[gBaGu]

1. Tracer doesn't count call opcode:
   In transact_call() gas recorded before calling tracer.start_call(). Is this an intended behaviour?

2. Tracer doesn't count refund:
   call_inner() is using self.gas_left() to calculate gas consumption for a trace but self.gas_left() doesn't count refunded gas which leads to trace with gas_used bigger then transaction used gas.

3. When setting gas_limit to exact gas amount transaction will use, transaction will fail if there will be refund during execution.