[eclipse-pmc] API Request: Support Servicability in ErrorDialog

[Tod Creasey <Tod_Creasey@xxxxxxxxxx>]

API Request

Add the following to JFace

New class: org.eclipse.jface.dialogs.ErrorSupportProvider.
A singleton used to provide the contents of a Composite on the left hand
side of ErrorDialogs to allow applications to plug-in thier own support
information.

New methods: 

int org.eclipse.jface.dialog.IconAndMessageDialog.getColumnCount()
   the number of columns in
GridLayout of the top level Shell

org.eclipse.jface.util.Policy 
   void setErrorProvider(ErrorSupportProvider).
Set the ErrorSupportProvider singleton
   ErrorSupportProvider
getErrorProvider(). Get the ErrorProvider singleton

RISKS
Existing error dialogs that re-implement
createDialogArea without calling super() will not get this support.
Existing error dialogs that hard code
the number of columns in thier button bar will no longer be right justified
when this support is installed.

RISKS OF NOT SUPPLYING THIS SUPPORT

ErrorDialogs will not be part of the
3.3 Servicability support and all explicit
calls to ErrorDialog and it's subclasses
will not provide this service.

Associated bug: 
https://bugs.eclipse.org/bugs/show_bug.cgi?id=175117