Allow to run tests in parallel.
Allow to run tests in parallel.

The test_interpreter script waste a lot of time in the kernel
process, that should be fixed. For know magic '-j' option allows
to speedup test execution a bit.

Change-Id: Ib1f0cbecc2053e434eb8df4e2e1edb22bc3e7846
Reviewed-by: Erik Verbruggen <5edfe905d082749f2ac3f4e6b42937f39f083771@digia.com>

matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative