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
private void updateEncodingState(boolean useDefault) {
        defaultEncodingButton.setSelection(useDefault);
        otherEncodingButton.setSelection(!useDefault);
        encodingCombo.setEnabled(!useDefault);
        updateValidState();
    }
    /**
     * The default button has been pressed. 
     */
    protected void performDefaults() {
        updateEncodingState(true);
        clearUserSettings = true;
        super.performDefaults();
    }
    /* (non-Javadoc)
     * @see org.eclipse.ui.internal.dialogs.FileEditorsPreferencePage#performOk()
     */
    public boolean performOk() {
        
    	String setting = null;
        if (!defaultEncodingButton.getSelection()) 
        	setting = encodingCombo.getText();
        
        if(clearUserSettings)
        	IDEEncoding.clearUserEncodings();
            
        IDEEncoding.setResourceEncoding(setting);
        return super.performOk();
    }
}