Allow anything to go inside accents

Fix #1217

Test:
``` nimrod

type
  Test = enum
    `1`, `3`, `{`, `(.`, `{}}{`, `*4&*$**()&*@`

let `.}` = 1
let `(}` = 2
let `[` = 3
let `]` = 5

echo `1`, `3`, `{`, `(.`, `{}}{`, `*4&*$**()&*@`, `.}`, `(}`, `[`, `]`
```