Fix parser for proper "redundant storage class" check

Current dmd parser reports "redundant storage class" error for such code:
```d
const const x = 1;
```

Recently I fixed [issue 9679](http://d.puremagic.com/issues/show_bug.cgi?id=9679) in #1937, but it did not support the "redundant storage class" check, and I found same issue in `foreach` statement.

This pull request fixes the two issues.