VCD input names are silently truncated to 1 char

The "abbreviated" names in the vcd file are silently truncated to 1 char.  So, if your input VCD file looks like:                                   
```
...
$scope module logic $end
$var wire 1 b0 pinB0 $end
$var wire 1 b1 pinB1 $end
...
#123
1b0
0b1
#456
0b0
1b1
...
```
you end up with only one pin being toggled with *no* indication that this is happening.