Sniper printer code formatting problems

I am testing Spoon on our project and there were a number of formatting changes (some with functional impact). I decided too check what happened when rewriting all elements in all files of our projects.

I used the following processor:
``` java
new AbstractProcessor() {
public void process(CtElement element) {
// Do a no-op change, this will force the sniper printer to update the source
SourcePosition pos = element.getPosition();
element.setPosition(SourcePosition.NOPOSITION);
element.setPosition(pos);
};
}
```

I checked the most important problems and made testcases for them.

The kind of problems:
- Brackets being removed/inserted
- Exception class names being fully qualified
- Comments in conditional statements being incorrectly handled
- Semicolon at end of enums being added
- Comments in enum arguments (causes crash)
- Comment formatting being changed

For details see tests in #3812

I suspect there are more issues, but these are the most frequent ones.