SI-7982 make askLoadedType unload arguments out of the PC by default,

Re-opened https://github.com/scala/scala/pull/3158 to target 2.10.x

review by @adriaanm

As point out by @huitseeker in https://github.com/scala/scala/pull/3158#issuecomment-28900230, scala-refactoring failure is expected until https://github.com/scala-ide/scala-refactoring/pull/37 is merged. I'm not sure what's the best course of action here, but merging this PR will require some coordination with @misto, because the scala-refactoring PR should be merged at the same time.