communications with numbers in channel name parse incorrectly

Given the following CML example

```
channels
  a : int * int
process P = begin @ a.1.2 -> P end
```

the COMPASS tool will produce a type error.  The problem is that the parser reads `a.1.2` as the channel named `a.(1.2)` rather than `a.(1).(2)` → i.e. the parser sees a real number when it ought (in this case) see two integers separated by dots.
