Store the last token parsed in the parser state so that the range parsed
can utilize its end rather than the start of the token after parsed.
This results in a tighter range (especially true in the case of
comments, see
```mlir
|%c4 = arith.constant 4 : index
// Foo
|
```
vs
```mlir
|%c4 = arith.constant 4 : index|
```
).
Discovered while working on a little textual post processing tool.
c1d02bd147