bug: JDTTreeBuilderQuery.searchTypeBinding can fail to find nested types

I stumbled upon this when working on #3707

In `JDTTreeBuilderQuery.searchTypeBinding`, there's this small part where it searches nested types of a type declaration.

https://github.com/INRIA/spoon/blob/f3d1677b725f88078812a4d61c5d8eb252a339da/src/main/java/spoon/support/compiler/jdt/JDTTreeBuilderQuery.java#L81-L87

The expression `qualifiedName.equals(CharOperation.toString(memberType.binding.compoundName))` is the problem, because `qualifiedName` is a dot-separated qualified name, while `CharOperation.toString(memberType.binding.compoundName)` will delimit nested types with `$`. For example, with this declaration:

```java
package pkg;

class Outer {
class Inner {}
}
```

`qualifiedName` will be `pkg.Outer.Inner`, whereas `CharOperation.toString(memberType.binding.compoundName)` will be `pkg.Outer$Inner`. The return statement in the middle is not covered by the test suite (see [the latest coverage report](https://coveralls.io/jobs/71160098/source_files/3781023179#L84)), so I suspect that it simply can't be hit.

This isn't hard to fix, I think I can get around to it sometime this week.