Add support for complex channel names in ASC files

### Is your feature request related to a problem? Please describe.
We encountered an ASC file that contains channels names like `Li`:
```
42.017364 Li 14 Rx 8 2a 79 00 00 00 80 c0 ff checksum = 07 header time = 40, full time = 135 SOF = 42.010348 BR = 19200 break = 942203 109234 EOH = 42.012418 EOB = 42.012979 42.013527 42.014075 42.014623 42.015172 42.015720 42.016268 42.016816 sim = 0 EOF = 42.017364 RBR = 19157 HBR = 19202.640363 HSO = 22785 RSO = 22837 CSM = enhanced
```
The current ASC reader fails to parse these files, i.e. it skips these messages because channel has to be an int.

### Describe the solution you'd like
Would it be possible to enhance the ASC reader to deal with the complex channel names?