[platform-core-dev] Changes to the Expression language

[Dirk Baeumer <dirk_baeumer@xxxxxxxxxx>]

I made the following changes to the expression language
(org.eclipse.core.expressions):

- removed the constructor

  public EvaluationContext(IEvaluationContext parent, Object
defaultVariable, Object selection)

  Instead of calling this constructor, the following code has to be
written:

EvaluationContext evalContext= new EvaluationContext(null, cunit);
evalContext.addVariable("selection", cunit); //$NON-NLS-1$

- removed the two string constants:
  public static final String SYSTEM= "System";  //$NON-NLS-1$
  public static final String SELECTION= "selection";  //$NON-NLS-1$

- added support for custom variable resolver (see new class
IVariableResolver). So there is no need
  to subclass EvaluationContext anymore to add your own resolving strategy.

- added support for an equals expression

I checked these changes against the nightly build Build id: 200403180010
and they don't cause any harm there.

Dirk