Bug 73082 [Encoding] Need an encoding extension point
We need to have an extension point for encodings. All it need have is the IDs of the encodings that are to be added to the list. It will require verification and indication of unavailable encodings.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/IDEEditorsPreferencePage.java
if(isDefault)
        	encodingCombo.setText(WorkbenchEncoding.getWorkbenchDefaultEncoding());
        else
        	encodingCombo.setText(resourcePreference);
        
        updateEncodingState(isDefault);
    }
    protected void updateValidState() {
        super.updateValidState();
        if (!isValid()) {
            return;
        }
        if (!isEncodingValid()) {
            setErrorMessage(IDEWorkbenchMessages
                    .getString("WorkbenchPreference.unsupportedEncoding")); 
            setValid(false);
        }
    }
    private boolean isEncodingValid() {
        return defaultEncodingButton.getSelection()
                || isValidEncoding(encodingCombo.getText());
    }
    private boolean isValidEncoding(String enc) {
        try {
            new String(new byte[0], enc);
            return true;
        } catch (UnsupportedEncodingException e) {
            return false;
        }
    }