Workaround delays in processing context menus by deferring MenuManager
updates.  This workaround is conditional on the
'eclipse.workaround.bug467000' system property being true.

Change-Id: Ida80e24773a4b866757e5ffd457183691e2343b1
Signed-off-by: Dirk Fauth <dirk.fauth@googlemail.com>