Support @Override annotation for role classes

[stephan]

Role classes, just like methods, override inherited versions simply based on name equality. For methods Java 5 introduced the @Override annotation for documenting overriding in the source code and for supporting compile time checks whether all overrides have been declared and whether all declared overrides are actually overrides.

In OT/J the same concept should be applied to role classes, too.

Furthermore the tool should display override markers for roles, too.

[stephan]

Should definitely do this. Haven't analyzed how difficult this is.

[stephan]

The UI issue (markers/indicators) has been separated into #220.

[stephan]

Tests are here

• A.1.16-otjld-override-annotation-1 (positive)
• A.1.16-otjld-override-annotation-2 (negative, not overriding)
• A.1.16-otjld-override-annotation-3 (negative, missing annotation)

r19754 brings

• definition in OTJLD §1.3.1(c)
• implementation

Note, that the warning can be configured together with method-override annotations (batch compiler uses token over-annon).