[jdt-core-dev] Heuristic for shrinking error messages did not work well

["Philippe Mulet" <Philippe_Mulet@xxxxxxx>]

There were a couple places where it was too naive (e.g. type imports were
loosing their package prefix, ...).

I had thus to replace it with the "real" implementation, passing along 2
sets of problem arguments (arguments for bookkeeping, arguments for
display).

Changes are released in HEAD, please raise issues caused by these changes.