ECJ treats non-local classes as local classes when considering modifiers

ECJ treats nested members of local classes as if they were local classes when considering allowed modifiers. For instance, consider:

```java
package test;

public class Test {
public static void main(String[] args) {
class LocalClass {
public class NotALocalClass {}
}
}
}
```

In this example, `LocalClass` is a local class but `NotALocalClass` is _not_; by the JLS:
> A local class is a nested class ([§8 (Classes)](https://docs.oracle.com/javase/specs/jls/se24/html/jls-8.html)) whose declaration is **immediately** contained by a block ([§14.2](https://docs.oracle.com/javase/specs/jls/se24/html/jls-14.html#jls-14.2)).

(from JLS [§14.3](https://docs.oracle.com/javase/specs/jls/se24/html/jls-14.html#jls-14.3); emphasis mine) which does not apply to `NotALocalClass`. Thus, `NotALocalClass` being public should not be an issue (and indeed javac compiles this without issue). However, ecj treats it as a local class for the purposes of determining if the `public` modifier is allowed here -- attempting to compile the example with the latest ecj (`3.42.50-SNAPSHOT`) gives:

```
1. ERROR in Test.java (at line 6)
public class NotALocalClass {}
^^^^^^^^^^^^^^
Illegal modifier for the local class NotALocalClass; only abstract or final is permitted
----------
```