message: Fix sampler slot extraction on gather4_po_c when debugging dxbc shader
  gather4_po_c has 6 operands and offset of sampler should be 4 instead of 3.
diff: @@ -4049,8 +4049,12 @@ State State::GetNext(GlobalState &global, State quad[4]) const
  UINT texSlot = (UINT)op.operands[2].indices[0].index;
  UINT sampSlot = 0;
  - if(op.operands.size() >= 4 && !op.operands[3].indices.empty())
  - sampSlot = (UINT)op.operands[3].indices[0].index;
  + for(size_t i = 0; i < op.operands.size(); i++)
  + {
  + const ASMOperand &operand = op.operands[i];
  + if(operand.type == OperandType::TYPE_SAMPLER)
  + sampSlot = (UINT)operand.indices[0].index;
  + }
  if(op.operation == OPCODE_SAMPLE || op.operation == OPCODE_SAMPLE_B ||
  op.operation == OPCODE_SAMPLE_D)
  