liteide_stub : do not try to include tests packages except at first level

For example find definition was broken if a package depends on
"github.com/Unknwon/goconfig" but the package
"github.com/smartystreets/goconvey/convey" is not installed.
Move withTests parameter to PkgConfig
Merge pull request #259 from vanackere/fix-find-def

liteide_stub : do not try to include tests packages except at first level